Forecast Discussions mentioning any of
"HRRR" "RAP" "RR" "RUC13" "RUC" received at GSD on 03/01/13
AREA FORECAST DISCUSSION
NWS DENVER/BOULDER CO
1006 AM MST WED FEB 27 2013
.UPDATE...
&&
.SHORT TERM...CURRENT FORECASTS LOOK ON TRACK. NORTHERLY FLOW
FINALLY WEAKENING ACROSS THE PLAINS WITH SURFACE OBS SHOWING WINDS
DECREASING THOUGH STILL SOME GUSTS AROUND 25 KTS. COULD REMAIN A
BIT GUSTY FAR EASTERN ZONES THROUGH THE AFTERNOON AS MODELS STILL
SHOW A NORTHERLY GRADIENT. SOME MOISTURE STILL TRAPPED ACROSS THE
MOUNTAINS...WITH WEB CAMS SHOWING SOME LIGHT SNOW ALONG THE RIDGES
OF SUMMIT AND GRAND COUNTIES. COULD ALSO BE SOME LIGHT SNOW OVER
THE PARK AND GORE RANGES OF JACKSON COUNTY. LATEST RAP CROSS
SECTIONS MAINTAIN SOME MOISTURE THERE THROUGH THE AFTERNOON ALONG
WITH MODEST LAPSE RATES AND OROGRAPHICS. WILL KEEP SOME LIGHT SNOW
THERE THROUGH THE DAY. ANY ACCUMULATIONS TO BE MINIMAL. SLIGHT
WARMING EXPECTED TODAY WITH GOOD SUNSHINE...THOUGH RECENT SNOWFALL
WILL SLOW PROGRESS.
.AVIATION...SKIES HAVE CLEARED ACROSS THE AREA AIRPORTS AS DRIER
AIR HAS SPREAD OVER THE REGION. LATEST MODELS SHOWING WINDS
SHIFTING TO THE NORTHWEST AROUND 18 OR 19Z WITH SPEEDS AROUND
8 KTS...THEN WEAKENING AROUND 21Z AND A BIT MORE NORTHERLY. RAP
AND HRRR SUGGESTING NORTHEAST TO EAST WINDS AFTER 21Z WITH THE
DEVELOPMENT OF A WEAK ANTICYCLONE. WITH NORTHWEST FLOW ALOFT...
UNSURE ABOUT THE ANTICYCLONE DEVELOPING AND WILL MAINTAIN THE
CURRENT TAF TRENDS.
&&
.PREV DISCUSSION... /ISSUED 444 AM MST WED FEB 27 2013/
UPDATE...
SHORT TERM...UPDATED TO REMOVE THE EXPIRATION OF THE ADVISORY
FROM PORTIONS OF THE PLAINS. 88D SHOWING LIGHT ECHOES RAPIDLY
DIMINISHING.
PREV DISCUSSION... /ISSUED 309 AM MST WED FEB 27 2013/
SHORT TERM...THE AREA OF SNOW ACROSS THE NORTHEAST PLAINS IS EVER
SO SLOWLY BEGINNING TO SHRINK IN COVERAGE. EARLIER HAD EXTENDED
THE ADVISORY UNTIL 4 AM AND THINK THAT SHOULD BE FINE. THERE
STILL MAY BE SOME AREAS OF VERY LIGHT SNOW THROUGH THE EARLY
MORNING HOURS BUT ANY ADDITIONAL ACCUMULATION WILL BE UNDER A HALF
INCH. THERE ARE STILL SOME GUSTY WINDS ON THE PLAINS BUT THESE
WINDS WILL ALSO DECREASE THIS MORNING AS THE SURFACE GRADIENT
RELAXES. STILL QUITE A BIT OF CLOUD COVER UPSTREAM SO HAVE DELAYED
SOME OF THE CLEARING THIS MORNING. A SLOW MODERATION OF
TEMPERATURES THIS AFTERNOON WITH MOSTLY SUNNY SKIES. FOR
TONIGHT...WILL SOME INCREASING MID AND HIGH LEVEL CLOUDS IN
ADVANCE OF NEXT SYSTEM.
LONG TERM...YET ANOTHER DISTURBANCE IN THE NORTHWEST FLOW ALOFT
WILL SWING DOWN OVER NORTHEAST COLORADO THURSDAY INTO FRIDAY.
THIS SYSTEM SHOULD MAINLY AFFECT THE MOUNTAINS IN THE FAVORED
FLOW...HOWEVER SOME MODELS ARE PICKING UP ON A POSSIBILITY OF A
FEW SHOWERS MOVING OVER THE PLAINS. OVERALL...MODEL AGREEMENT IS
POOR ON THE UPPER LEVELS OF THIS DISTURBANCE...AND NORTHWEST FLOW
IS USUALLY MORE OF A DOWNSLOPE PATTERN FOR THE PLAINS. HOWEVER
CANNOT IGNORE ABOUT HALF OF THE MODELS VIEWED SHOWING LIGHT
PRECIPITATION. RUN TO RUN CONSISTENCY IS NOT THE BEST WITH THIS
PIECE OF ENERGY...WITH TIMING DIFFERENCES WITH EACH NEW RUN. THE
BEST TIME FRAME HOWEVER LOOKS TO BE THURSDAY EVENING FOR A FEW
SHOWERS OVER THE PLAINS. OTHERWISE...SNOW WILL BE INCREASING OVER
THE MOUNTAINS THROUGH THE DAY THURSDAY AND INTO THE NIGHT...BEFORE
EASING OFF FRIDAY. ACCUMULATIONS OVER THE MOUNTAINS WILL MAINLY BE
OROGRAPHICALLY DRIVEN...LEAVING THE HIGHEST AMOUNTS ON WEST TO
NORTHWEST FACING SLOPES. CURRENTLY EXPECT 3 TO 6 INCHES THURSDAY
THROUGH FRIDAY AFTERNOON. THURSDAY TEMPERATURES WILL BE SIMILAR TO
TODAYS WITH ONLY A DEGREE OR TWO OF WARMING. FRIDAY WILL SEE
TEMPERATURES WARM EVEN MORE WITH THE PLAINS FINALLY REACHING INTO
THE LOW 40S AND THE MOUNTAINS IN THE 20S. NORTHWESTERLY SURFACE WINDS
WILL BE INCREASING THURSDAY AND INTO FRIDAY AS A 115 KT N TO S JET
MOVES OVERHEAD AND AIDED BY SURFACE PRESSURE GRADIENT FROM HIGH
PRESSURE OVER SW WYOMING AND LOWER PRESSURE OVER TEXAS. NO
HIGHLIGHTS ARE NEEDED. GUSTS MAY REACH 40 TO 50 MPH IN THE
FOOTHILLS AND UP TO 30 MPH OVER THE PLAINS THURSDAY NIGHT INTO
FRIDAY.
FRIDAY NIGHT INTO SUNDAY AFTERNOON...AN UPPER RIDGE BUILDS
OVERHEAD TO BRING WARMER AND DRIER CONDITIONS. TEMPERATURES ARE
EXPECTED TO RETURN TO NEAR NORMAL READINGS WITH UPPER 40S TO LOW
50S FOR THE PLAINS AND 30S TO LOW 40S FOR THE MOUNTAINS.
SUNDAY NIGHT AND INTO MONDAY IS THE NEXT CHANCE FOR MORE
PRECIPITATION FOR THE FORECAST AREA. MODELS SHOWING A PACIFIC
NORTHWEST SYSTEM DIGGING SOUTHEAST TOWARD THE AREA SUNDAY
NIGHT...HOWEVER WITH A DEEPER AND SLOWER SOLUTION SHOWN BY THE
ECMWF AND A WEAKER AND MORE PROGRESSIVE SOLUTION BY THE GFS...AND
AN EVEN MORE PROGRESSIVE SOLUTION BY THE CANADIAN MODEL. WILL KEEP
THE CHANCE OF SNOW FOR THE MOUNTAINS SUNDAY NIGHT INTO MONDAY AND
PUT A SLIGHT CHANCE FOR THE PLAINS SUNDAY NIGHT AS MODELS SHOWING
SOME SORT OF COLD FRONT MARCHING DOWN THEN.
THEN YET ANOTHER UPPER RIDGE WILL BUILD IN MONDAY EVENING INTO
WEDNESDAY FOR ANOTHER WARMING AND DRYING TREND.
AVIATION...MID LEVEL DECK OF CLOUDS IN THE 6000 TO 8000 FT AGL
LEVEL WILL HANG THRU MID MORNING GIVEN THE OBSERVATIONS TO THE
NORTHWEST ACROSS WYOMING. SKIES WILL BECOME MOSTLY SUNNY THIS
AFTERNOON. NORTH TO NORTHWEST SURFACE WINDS WILL PERSIST THIS
MORNING BUT SPEEDS GENERALLY UNDER 15KT.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...D-L
LONG TERM....KRIEDERMAN
AVIATION...D-L
AREA FORECAST DISCUSSION
NWS PUEBLO CO
150 AM MST WED FEB 27 2013
.UPDATE...
ISSUED AT 141 AM MST WED FEB 27 2013
ALTHOUGH STARTING TO TREND DOWNWARD...SNOW AND BLOWING SNOW CONTINUES
OVER THE PALMER DIVIDE. EXTENDED WINTER WEATHER ADVISORY FOR SNOW
AND BLOWING SNOW FOR THE DIVIDE THROUGH 5 AM. UPDATED SHORT TERM
FORECASTS TO REFLECT CURRENT OBSERVATIONS AND TRENDS. LW
UPDATE ISSUED AT 1022 PM MST TUE FEB 26 2013
SNOW GRADUALLY WINDING DOWN OVER NORTHERN EL PASO COUNTY...THOUGH
STILL A COUPLE MORE NARROW BANDS OF AT LEAST BRIEFLY MODERATE
SNOW POSSIBLE OVER EXTREME NERN PART OF THE COUNTY AS AREA OF
HIGHER REFLECTIVITY EAST OF DENVER METRO ROTATES SOUTH. EXPECT ANY
ADDITIONAL ACCUMULATIONS TO BE GENERALLY AN INCH OR LESS. WINDS
STILL GUSTING 25-35 KNOTS FROM KFLY AND KMNH EAST TO KLIC...AND
LATEST HRRR KEEPS GUSTS IN THE 25-30 KT RANGE UNTIL AROUND 09Z-
10Z. WILL KEEP ADVISORY IN PLACE UNTIL 09Z...AS LOCAL MEDIA/ROAD
REPORTS CONTINUE TO INDICATE VERY DIFFICULT TRAVEL EAST/NORTHEAST
OF COLORADO SPRINGS DUE TO LOW VIS AND DRIFTING SNOW.
ELSEWHERE...LIGHT SNOW WILL CONTINUE A FEW MORE HOURS MAINLY SOUTH
OF THE ARKANSAS RIVER AND OVER THE WETS/SANGRES...THOUGH
ADDITIONAL ACCUMS HERE LOOK LIGHT...LESS THAN AN INCH.
UPDATE ISSUED AT 740 PM MST TUE FEB 26 2013
ISSUED A SHORT FUSED WINTER WEATHER ADVISORY FOR NORTHERN EL PASO
COUNTY...AS WINDS HAVE INCREASED AND BANDS OF MODERATE TO HEAVY
SNOW CONTINUE TO ROTATE SOUTH. LATEST HRRR KEEPS PRECIP GOING UNTIL
08Z...AND SHOWS WIND GUSTS OVER 30 KTS NEAR THE PALMER DIVIDE
UNTIL AT LEAST 10Z. HAVE HAD NUMEROUS REPORTS OF ROAD
CLOSURES/DIFFICULT TRAVEL DUE TO WIDESPREAD BLOWING/DRIFTING SNOW
NORTH AND EAST OF COS. FORECASTS FOR THE REMAINDER OF THE AREA
WERE REFRESHED TO ACCOUNT FOR ONGOING PRECIP.
&&
.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 325 PM MST TUE FEB 26 2013
SHORT TERM METEOROLOGICAL ISSUES INCLUDE BUT ARE NOT LIMITED TO
POPS/SNOW AMOUNTS...WINDS AND TEMPERATURES. FORECAST DISTRICT
CURRENTLY NOTING SNOW ACTIVITY...ESPECIALLY OVER THE MOUNTAINS AND
HIGHER TERRAIN AREAS AS WELL AS OVER MANY PORTIONS OF THE I-25
CORRIDOR AS WELL AS AREAS OF GUSTY NORTH WINDS.
AS OF 3 PM MST...REPORTED SNOW AMOUNTS HAVE GENERALLY BEEN
UNDER 4 INCHES...I.E RECENTLY RECEIVED A SPOTTER SNOW REPORT OF
3.5 INCHES OF SNOW 11 MILES TO THE NORTH-NORTHEAST OF CRESTONE IN
CUSTER COUNTY(PUBLIC ZONE 72) WITH LIGHT SNOW CONTINUING.
LATEST SHORT/NEAR-TERM COMPUTER SIMULATIONS...FORECAST MODEL
SOUNDINGS AND REAL-TIME DATA INDICATE THAT THE UPPER DISTURBANCE
WILL CONTINUE TO IMPACT MANY SECTIONS OF THE CWFA INTO TONIGHT
BEFORE SHIFTING EAST OF THE FORECAST DISTRICT BY WEDNESDAY MORNING.
STILL EXPECT THAT 4 TO 8 INCH SNOW TOTALS(INCLUDING SNOW THAT HAS
ALREADY FALLEN EARLIER TODAY...I.E. 12 TO 18 HOUR TIME-RANGE) WILL
BE POSSIBLE OVER MANY MOUNTAIN AND HIGHER FOOTHILL LOCATIONS WITH
2 TO 5 INCHES OF SNOW OVER NORTHERN EL PASO COUNTY AND 2 INCHES OR
LESS OF SNOW ELSEWHERE WILL BE NOTED BEFORE THIS EVENT ENDS LATER
TONIGHT. IN ADDITION...A FEW LOCALLY HIGHER SNOW AMOUNTS WILL ALSO
BE POSSIBLE BY SUNRISE WEDNESDAY.
IN ADDITION TO THE SNOW FROM THIS AFTERNOON INTO TONIGHT...GUSTY
NORTH WINDS AT TIMES ARE ALSO EXPECTED IN COMBINATION WITH CONTINUED
BELOW SEASONAL LATE FEBRUARY TEMPERATURES.
FOR WEDNESDAY...AS UPPER SYSTEM DEPARTS SOUTHERN
COLORADO...ANTICIPATE THAT GENERALLY DRY CONDITIONS IN COMBINATION
WITH CLEARING SKIES...DECREASING WINDS(EXCEPT FOR POSSIBLY FAR
EASTERN SECTIONS) AND WARMER TEMPERATURES(ALTHOUGH STILL BELOW LATE
FEBRUARY CLIMATOLOGICAL AVERAGES) WILL BE NOTED ACROSS THE FORECAST
DISTRICT.
.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 325 PM MST TUE FEB 26 2013
WED NIGHT...GENERALLY DRY NW FLOW ALOFT WL BE OVR THE AREA...BUT
THERE COULD BE A FEW SHOWERS OVR THE CONTDVD MAINLY IN THE EVENING
HOURS. FORECAST MODELS DO NOT AGREE ON THE WEATHER FOR LATE THU AND
THU NIGHT. THE GFS HAS THE AREA MOSTLY DRY INTO THE EARLY
AFTERNOON...BUT LATE IN THE AFTERNOON A SHORTWAVE TROF DROPS INTO
SWRN WY AND AHEAD OF THIS SYSTEM...WITH MOISTURE INCREASING AND THE
GFS BRINGS CHANCES FOR SNOW TO THE CENTRAL MTS AND TO THE PIKES PEAK
TELLER COUNTY REGION. THEN THU NIGHT THAT SYSTEM DROP SOUTH THU
CO...SPREADING PCPN CHANCES SOUTHWARD AS WELL. THE NAM AND THE ECMWF
DO NOT HAVE THIS SHORTWAVE TROF AND IS KEEPING THE WEATHER DRY. WL
STICK WITH SOME PCPN IN THE CENTRAL MTS...WITH MAYBE JUST A FEW
SHOWERS OVR THE OTHER MTN PEAKS AND SEE WHAT FUTURE MODEL RUNS BRING.
FRI...AS AN UPR LOW DROPS INTO WRN MO AND ERN KS A FRONT BRING
SOME BREEZY NORTHERLY WINDS TO MUCH OF THE EASTERN CO PLAINS. THE
NAM IS MOSTLY DRY OVR THE AREA FOR FRI...WHILE THE GFS AND ECMWF
BOTH SHOW SOME POTENTIAL FOR PCPN OVR THE MTS AND ERN PLAINS. AN
UPR RIDGE THEN BUILD OVR THE AREA FOR THE WEEKEND...RESULTING IN
DRY WEATHER AND WARMER TEMPS. LATE SUN THE UPR RIDGE GETS
FLATTENED OVR THE AREA AS A NEW UPR LOW MOVES INTO WRN MT. THE
TRACK OF THAT UPR LOW IS THEN QUITE UNCERTAIN AS THE GFS BRINGS IT
SOUTHEASTWARD AND ACRS NORTHEAST CO BY MIDDAY MON WHILE THE ECMWF
STILL HAS IT OVR MT. BY 06Z TUE THE GFS MOVES THE LOW INTO NRN
MO...WHILE THE ECMWF HAS IT OVR SRN MT AND NRN WY. THUS ITS HARD
TO SAY EXACTLY WHAT IS IN STORE FOR THE FORECAST AREA SUN NIGHT
AND MON BUT FOR NOW BOTH MODELS AT LEAST HAVE SOME PCPN OVR THE
CENTRAL MTS. WL PROBABLY SEE A SHORTWAVE RIDGE AND MAINLY DRY
WEATHER OVR THE AREA ON TUE.
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1022 PM MST TUE FEB 26 2013
AT KCOS...STILL A FEW LIGHT -SHSN IN THE AREA AS OF 0530Z...THOUGH
INTENSITY HAS BEEN DECREASING THE LAST COUPLE HOURS. WILL CARRY
-SN IN THE TAF UNTIL AROUND 08Z...ALONG WITH OCCASIONAL MVFR VIS IN
BLOWING SNOW AS GUSTY NORTH WINDS PERSIST. VFR CONDITIONS THEN
EXPECTED FROM EARLY MORNING THROUGH THE DAY WEDNESDAY AS UPPER
SYSTEM PULLS AWAY. NORTH WINDS WILL DIMINISH THROUGH THE
MORNING...GRADUALLY TURNING TO THE SOUTH BY AFTERNOON.
AT KPUB AND KALS...KEPT A MENTION OF VCSH UNTIL 08Z...THOUGH ANY
-SHSN WILL BE VERY BRIEF AND HAVE LITTLE IMPACT. NORTH WINDS WILL
REMAIN GUSTY UNTIL 10-12Z...THEN DIMINISH. ON TUES...EXPECT VFR
CONDITONS WITH MUCH LIGHTER WINDS.
MOUNTAINS AND PALMER DIVIDE WILL CONTINUE TO BE OBSCURRED BY LOW
CLOUDS AND -SHSN THROUGH THE NIGHT...THEN SNOW ENDS AND SKIES
GRADUALLY CLEAR AROUND SUNRISE. OVER THE PLAINS...ISOLATED MVFR
CIGS/VIS IN -SHSN WILL COME TO AND END 08Z-10Z WITH VFR MOST AREAS
BY 12Z.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 5 AM MST EARLY THIS MORNING FOR
COZ084.
&&
$$
UPDATE...LW
SHORT TERM...77
LONG TERM...28
AVIATION...PETERSEN
AREA FORECAST DISCUSSION
NWS PUEBLO CO
1039 PM MST TUE FEB 26 2013
.UPDATE...
ISSUED AT 1022 PM MST TUE FEB 26 2013
SNOW GRADUALLY WINDING DOWN OVER NORTHERN EL PASO COUNTY...THOUGH
STILL A COUPLE MORE NARROW BANDS OF AT LEAST BRIEFLY MODERATE
SNOW POSSIBLE OVER EXTREME NERN PART OF THE COUNTY AS AREA OF
HIGHER REFLECTIVITY EAST OF DENVER METRO ROTATES SOUTH. EXPECT ANY
ADDITIONAL ACCUMULATIONS TO BE GENERALLY AN INCH OR LESS. WINDS
STILL GUSTING 25-35 KNOTS FROM KFLY AND KMNH EAST TO KLIC...AND
LATEST HRRR KEEPS GUSTS IN THE 25-30 KT RANGE UNTIL AROUND 09Z-
10Z. WILL KEEP ADVISORY IN PLACE UNTIL 09Z...AS LOCAL MEDIA/ROAD
REPORTS CONTINUE TO INDICATE VERY DIFFICULT TRAVEL EAST/NORTHEAST
OF COLORADO SPRINGS DUE TO LOW VIS AND DRIFTING SNOW.
ELSEWHERE...LIGHT SNOW WILL CONTINUE A FEW MORE HOURS MAINLY SOUTH
OF THE ARKANSAS RIVER AND OVER THE WETS/SANGRES...THOUGH
ADDITIONAL ACCUMS HERE LOOK LIGHT...LESS THAN AN INCH.
UPDATE ISSUED AT 740 PM MST TUE FEB 26 2013
ISSUED A SHORT FUSED WINTER WEATHER ADVISORY FOR NORTHERN EL PASO
COUNTY...AS WINDS HAVE INCREASED AND BANDS OF MODERATE TO HEAVY
SNOW CONTINUE TO ROTATE SOUTH. LATEST HRRR KEEPS PRECIP GOING UNTIL
08Z...AND SHOWS WIND GUSTS OVER 30 KTS NEAR THE PALMER DIVIDE
UNTIL AT LEAST 10Z. HAVE HAD NUMEROUS REPORTS OF ROAD
CLOSURES/DIFFICULT TRAVEL DUE TO WIDESPREAD BLOWING/DRIFTING SNOW
NORTH AND EAST OF COS. FORECASTS FOR THE REMAINDER OF THE AREA
WERE REFRESHED TO ACCOUNT FOR ONGOING PRECIP.
&&
.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 325 PM MST TUE FEB 26 2013
SHORT TERM METEOROLOGICAL ISSUES INCLUDE BUT ARE NOT LIMITED TO
POPS/SNOW AMOUNTS...WINDS AND TEMPERATURES. FORECAST DISTRICT
CURRENTLY NOTING SNOW ACTIVITY...ESPECIALLY OVER THE MOUNTAINS AND
HIGHER TERRAIN AREAS AS WELL AS OVER MANY PORTIONS OF THE I-25
CORRIDOR AS WELL AS AREAS OF GUSTY NORTH WINDS.
AS OF 3 PM MST...REPORTED SNOW AMOUNTS HAVE GENERALLY BEEN
UNDER 4 INCHES...I.E RECENTLY RECEIVED A SPOTTER SNOW REPORT OF
3.5 INCHES OF SNOW 11 MILES TO THE NORTH-NORTHEAST OF CRESTONE IN
CUSTER COUNTY(PUBLIC ZONE 72) WITH LIGHT SNOW CONTINUING.
LATEST SHORT/NEAR-TERM COMPUTER SIMULATIONS...FORECAST MODEL
SOUNDINGS AND REAL-TIME DATA INDICATE THAT THE UPPER DISTURBANCE
WILL CONTINUE TO IMPACT MANY SECTIONS OF THE CWFA INTO TONIGHT
BEFORE SHIFTING EAST OF THE FORECAST DISTRICT BY WEDNESDAY MORNING.
STILL EXPECT THAT 4 TO 8 INCH SNOW TOTALS(INCLUDING SNOW THAT HAS
ALREADY FALLEN EARLIER TODAY...I.E. 12 TO 18 HOUR TIME-RANGE) WILL
BE POSSIBLE OVER MANY MOUNTAIN AND HIGHER FOOTHILL LOCATIONS WITH
2 TO 5 INCHES OF SNOW OVER NORTHERN EL PASO COUNTY AND 2 INCHES OR
LESS OF SNOW ELSEWHERE WILL BE NOTED BEFORE THIS EVENT ENDS LATER
TONIGHT. IN ADDITION...A FEW LOCALLY HIGHER SNOW AMOUNTS WILL ALSO
BE POSSIBLE BY SUNRISE WEDNESDAY.
IN ADDITION TO THE SNOW FROM THIS AFTERNOON INTO TONIGHT...GUSTY
NORTH WINDS AT TIMES ARE ALSO EXPECTED IN COMBINATION WITH CONTINUED
BELOW SEASONAL LATE FEBRUARY TEMPERATURES.
FOR WEDNESDAY...AS UPPER SYSTEM DEPARTS SOUTHERN
COLORADO...ANTICIPATE THAT GENERALLY DRY CONDITIONS IN COMBINATION
WITH CLEARING SKIES...DECREASING WINDS(EXCEPT FOR POSSIBLY FAR
EASTERN SECTIONS) AND WARMER TEMPERATURES(ALTHOUGH STILL BELOW LATE
FEBRUARY CLIMATOLOGICAL AVERAGES) WILL BE NOTED ACROSS THE FORECAST
DISTRICT.
.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 325 PM MST TUE FEB 26 2013
WED NIGHT...GENERALLY DRY NW FLOW ALOFT WL BE OVR THE AREA...BUT
THERE COULD BE A FEW SHOWERS OVR THE CONTDVD MAINLY IN THE EVENING
HOURS. FORECAST MODELS DO NOT AGREE ON THE WEATHER FOR LATE THU AND
THU NIGHT. THE GFS HAS THE AREA MOSTLY DRY INTO THE EARLY
AFTERNOON...BUT LATE IN THE AFTERNOON A SHORTWAVE TROF DROPS INTO
SWRN WY AND AHEAD OF THIS SYSTEM...WITH MOISTURE INCREASING AND THE
GFS BRINGS CHANCES FOR SNOW TO THE CENTRAL MTS AND TO THE PIKES PEAK
TELLER COUNTY REGION. THEN THU NIGHT THAT SYSTEM DROP SOUTH THU
CO...SPREADING PCPN CHANCES SOUTHWARD AS WELL. THE NAM AND THE ECMWF
DO NOT HAVE THIS SHORTWAVE TROF AND IS KEEPING THE WEATHER DRY. WL
STICK WITH SOME PCPN IN THE CENTRAL MTS...WITH MAYBE JUST A FEW
SHOWERS OVR THE OTHER MTN PEAKS AND SEE WHAT FUTURE MODEL RUNS BRING.
FRI...AS AN UPR LOW DROPS INTO WRN MO AND ERN KS A FRONT BRING
SOME BREEZY NORTHERLY WINDS TO MUCH OF THE EASTERN CO PLAINS. THE
NAM IS MOSTLY DRY OVR THE AREA FOR FRI...WHILE THE GFS AND ECMWF
BOTH SHOW SOME POTENTIAL FOR PCPN OVR THE MTS AND ERN PLAINS. AN
UPR RIDGE THEN BUILD OVR THE AREA FOR THE WEEKEND...RESULTING IN
DRY WEATHER AND WARMER TEMPS. LATE SUN THE UPR RIDGE GETS
FLATTENED OVR THE AREA AS A NEW UPR LOW MOVES INTO WRN MT. THE
TRACK OF THAT UPR LOW IS THEN QUITE UNCERTAIN AS THE GFS BRINGS IT
SOUTHEASTWARD AND ACRS NORTHEAST CO BY MIDDAY MON WHILE THE ECMWF
STILL HAS IT OVR MT. BY 06Z TUE THE GFS MOVES THE LOW INTO NRN
MO...WHILE THE ECMWF HAS IT OVR SRN MT AND NRN WY. THUS ITS HARD
TO SAY EXACTLY WHAT IS IN STORE FOR THE FORECAST AREA SUN NIGHT
AND MON BUT FOR NOW BOTH MODELS AT LEAST HAVE SOME PCPN OVR THE
CENTRAL MTS. WL PROBABLY SEE A SHORTWAVE RIDGE AND MAINLY DRY
WEATHER OVR THE AREA ON TUE.
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1022 PM MST TUE FEB 26 2013
AT KCOS...STILL A FEW LIGHT -SHSN IN THE AREA AS OF 0530Z...THOUGH
INTENSITY HAS BEEN DECREASING THE LAST COUPLE HOURS. WILL CARRY
-SN IN THE TAF UNTIL AROUND 08Z...ALONG WITH OCCASIONAL MVFR VIS IN
BLOWING SNOW AS GUSTY NORTH WINDS PERSIST. VFR CONDITIONS THEN
EXPECTED FROM EARLY MORNING THROUGH THE DAY WEDNESDAY AS UPPER
SYSTEM PULLS AWAY. NORTH WINDS WILL DIMINISH THROUGH THE
MORNING...GRADUALLY TURNING TO THE SOUTH BY AFTERNOON.
AT KPUB AND KALS...KEPT A MENTION OF VCSH UNTIL 08Z...THOUGH ANY
-SHSN WILL BE VERY BRIEF AND HAVE LITTLE IMPACT. NORTH WINDS WILL
REMAIN GUSTY UNTIL 10-12Z...THEN DIMINISH. ON TUES...EXPECT VFR
CONDITONS WITH MUCH LIGHTER WINDS.
MOUNTAINS AND PALMER DIVIDE WILL CONTINUE TO BE OBSCURRED BY LOW
CLOUDS AND -SHSN THROUGH THE NIGHT...THEN SNOW ENDS AND SKIES
GRADUALLY CLEAR AROUND SUNRISE. OVER THE PLAINS...ISOLATED MVFR
CIGS/VIS IN -SHSN WILL COME TO AND END 08Z-10Z WITH VFR MOST AREAS
BY 12Z.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 2 AM MST WEDNESDAY FOR COZ084.
&&
$$
UPDATE...MW
SHORT TERM...77
LONG TERM...28
AVIATION...PETERSEN
AREA FORECAST DISCUSSION
NWS TAMPA BAY RUSKIN FL
900 PM EST THU FEB 28 2013
.UPDATE (TONIGHT AND FRIDAY)...
01Z WATER VAPOR AND H4 RAP ANALYSIS SHOW THE NORTHERN STREAM FLOW
ARRIVING OVER THE PACIFIC NORTHWEST/BRITISH COLUMBIA BEFORE CARVING
OUT A BROAD LONGWAVE TROUGH FROM THE CONTINENTAL DIVIDE EASTWARD
THROUGH MUCH OF THE CONUS. UPPER LEVEL ENERGY WILL DIVE DOWN THE
BACK SIDE OF THIS LONGWAVE TROUGH DURING THE NEXT 24-36 HOURS AND
RESULT IN A SUBSTANTIAL AMPLIFICATION TO THE FLOW OVER THE EASTERN
HALF OF THE NATION. THIS AMPLIFICATION WILL IN PART DELIVER A MUCH
COLDER AIRMASS TO THE FL PENINSULA FOR THE UPCOMING WEEKEND.
CURRENTLY SEEING AN UPPER LEVEL JET ALIGNED ALONG AND JUST NORTH
OF THE NORTHERN GULF COAST RESULTING IN SUSTAINED DYNAMICS TO
SUPPORT A LARGE AREA OF HIGH LEVEL CLOUDS OVER THE I-10 CORRIDOR.
SOME OF THIS HIGHER CLOUD-COVER WILL SETTLE SOUTHWARD TO INVADE THE
NATURE COAST SKIES LATER TONIGHT INTO FRIDAY.
AT THE SURFACE...WEAK AND UNDEFINED FRONTAL BOUNDARY LIES NEAR THE
SOUTHERN FL PENINSULA/FLORIDA STRAITS. UNTIL THE UPPER LEVEL
AMPLIFICATION DESCRIBED ABOVE OCCURS...OUR LOCAL WEATHER THROUGH
FRIDAY WILL FEATURE GENERALLY DRY AND SEASONABLE TO SLIGHTLY BELOW
AVERAGE TEMPS. THEREAFTER INTO SATURDAY AND SUNDAY...TEMPERATURES
WILL FALL WELL BELOW AVERAGE.
&&
.AVIATION...
VFR THROUGH THE PERIOD AS CLOUDS INCREASE FRI...MAINLY MID AND HIGH.
NORTHWESTERLY AND NORTHERLY WINDS AT NO MORE THAN 13KT.
&&
.MARINE...
COLD AIR ADVECTION OVER THE RELATIVELY WARMER GULF WATERS WILL
RESULT IN FAIRLY STRONG NORTHWESTERLY WINDS THROUGH THE WEEKEND WITH
PERIODS OF EXERCISE CAUTION AND POSSIBLY ADVISORY HEADLINES NEEDED.
HIGH PRESSURE WILL SETTLE OVER THE REGION EARLY NEXT WEEK...WITH
IMPROVING CONDITIONS EXPECTED OVER THE MARINE AREA.
&&
.PRELIMINARY POINT TEMPS/POPS...
TPA 50 64 49 62 / 0 0 30 30
FMY 53 70 50 68 / 0 10 30 40
GIF 48 68 44 63 / 0 0 10 20
SRQ 53 65 52 63 / 0 10 30 50
BKV 42 63 41 61 / 0 0 20 30
SPG 55 63 53 62 / 0 10 30 40
&&
.TBW WATCHES/WARNINGS/ADVISORIES...
FL...BEACH HAZARDS STATEMENT FROM LATE FRIDAY NIGHT THROUGH
MONDAY AFTERNOON FOR CHARLOTTE-LEE-SARASOTA.
GULF WATERS...NONE.
&&
$$
UPDATE...MROCZKA
AVIATION...RUDE
AREA FORECAST DISCUSSION
NWS MELBOURNE FL
359 AM EST WED FEB 27 2013
.DISCUSSION...
TODAY-TONIGHT...COOL FRONT NEAR OKEECHOBEE SHOULD ONLY SLIDE A
LITTLE MORE TO THE SOUTH AS IT BECOMES NEARLY ALIGNED WITH FLOW
ALOFT. THE MODELS ARE SHOWING AN AREA OF RAINFALL BREAKING OUT
ACROSS THE SOUTHERN PENINSULA AS MOISTURE OVERRUNS THE BOUNDARY.
HOW FAR NORTH THIS OCCURS IS PROBLEMATIC.
THE GFS IS QUITE BULLISH WITH 60 POPS IN MARTIN COUNTY AND EVEN
30 PERCENT ALL THE WAY UP TO BREVARD...WHILE THE NAM HAS VALUES
ABOUT HALF THAT. WILL SIDE CLOSE TO THE NAM AS CURRENTLY THE ONLY
RAINFALL IS OVER FLORIDA BY AND FEEL MOST OF THE PRECIP SHOULD BE
FROM LAKE OKEECHOBEE SOUTHWARD.
MAX TEMPS WILL BE 5-10 DEGREES COOLER THAN YESTERDAY. DEW POINTS
WILL BE NOTICEABLY LOWER ESPECIALLY ACROSS THE NORTH HALF. THE
FRONTAL BOUNDARY WILL SLIDE FARTHER SOUTH TONIGHT WHICH WILL
ALLOW LOWS TONIGHT TO COOL A LITTLE FURTHER...INTO THE MID-UPPER
40S NORTH AND LOWER 50S SOUTH.
THU-FRI...ZONAL FLOW ALOFT EXPECTED OVER THE AREA INTO LATE WEEK
WITH DEEP LOW PRESSURE SYSTEM EVENTUALLY MOVING OFFSHORE OF THE
NORTHEAST U.S. COAST. LOW LEVEL NORTHWEST FLOW WILL CONTINUE TO
TRANSPORT DRIER AND COOLER AIR INTO CENTRAL FLORIDA. HIGHS THURSDAY
EXPECTED TO BE IN THE LOW/MID 70S AND THEN IN THE MID/UPPER 60S
FRIDAY. LOWS FORECAST TO RANGE FROM THE MID 40S TO LOW 50S THURSDAY
NIGHT AND LOW/MID 40S FRIDAY NIGHT. MAY SEE SOME GREATER CLOUD COVER
OVER THE AREA FRIDAY AS GFS INDICATES AN INCREASING MID/UPPER LEVEL
CLOUD DECK OVER THE REGION ASSOCIATED WITH STRONG 150+ KT JET OVER
THE SOUTHEAST UNITED STATES.
SAT-SUN...VIGOROUS SHORTWAVE TROUGH WILL DIG SOUTHWARD INTO THE
GULF OF MEXICO SATURDAY AND ACROSS FLORIDA SAT NIGHT INTO SUNDAY.
LOW LEVEL FLOW WILL REMAIN OUT OF THE W/NW WHICH WILL CONTINUE
GRADUAL COOLING INTO THE WEEKEND. TEMPERATURES WILL BE 10 TO 15
DEGREES BELOW NORMAL AND COULD POTENTIALLY SEE LOWS NEAR FREEZING
OVER FAR NORTHERN LAKE AND VOLUSIA COUNTIES LATE SUNDAY NIGHT.
THE OVERALL AIRMASS WILL REMAIN QUITE DRY WITH PW VALUES AROUND 0.50
INCHES OR LESS. DESPITE THIS THE GFS EXTENDED GUIDANCE KEEPS 20-30
PERCENT POPS OVER THE REGION...DUE TO STRONG TROUGH MOVING THROUGH
THE AREA AND INCREASING LOW LEVEL MOISTURE. STILL FEEL THESE POPS
ARE TOO HIGH...ESPECIALLY WITH THE GFS AND ECMWF NOT SHOWING ANY QPF
OVER EAST CENTRAL FLORIDA. WILL LEAN TOWARD THE ECMWF MOS GUIDANCE
AND KEEP A DRY FORECAST OVER THE AREA.
MON-TUE...UPPER LEVEL TROUGH PUSHES EAST OF THE AREA INTO EARLY NEXT
WEEK WITH HIGH PRESSURE AT THE SURFACE EVENTUALLY BUILDING OVER
FLORIDA. BELOW NORMAL TEMPERATURES EXPECTED TO CONTINUE INTO MON/MON
NIGHT WITH TEMPERATURES WARMING BACK INTO THE 70S TUESDAY. DRY
AIRMASS REMAINS OVER THE AREA...KEEPING RAIN CHANCES OUT OF THE
FORECAST.
&&
.AVIATION...
SOME MVFR CEILINGS HAVE BEEN OCCURRING EARLY THIS MORNING
ESPECIALLY IN THE SOUTH NEAR SLOW MOVING FRONTAL BOUNDARY. DRIER
AIR SLOWLY FILTERING IN SHOULD BRING VFR LATER THIS MORNING.
MVFR CEILINGS MAY RETURN OVER SOUTHERN AREAS BY AFTERNOON AS
MOISTURE OVERRUNS THE FRONTAL BOUNDARY...MAINLY KFPR-KSUA. THERE
COULD ALSO BE SOME LIGHT RAIN THERE.
&&
.MARINE...
TODAY-TONIGHT...WINDS AT 41009 FINALLY PICKED UP TO ADVISORY
LEVELS IN THE LAST FEW HOURS. SHORT RANGE GUIDANCE INDICATES A
WEAKENING PRESSURE GRADIENT BY LATE THIS MORNING AS HIGH PRESSURE
RIDGE NOSES IN BEHIND SLOW MOVING FRONTAL BOUNDARY THAT WILL
SETTLE JUST SOUTH OF THE WATERS.
DUE TO RECENT BUOY TRENDS...WILL EXTEND THE ADVISORY A LITTLE
LONGER FOR THE OFFSHORE WATERS. THE RAP AND LOCAL WRF MODELS SHOW
THE 20 KNOT WINDS ABATING AROUND 9 AM. WINDS SHOULD THEN DROP
BELOW 10 KNOTS THIS AFTERNOON AND INTO EARLY EVENING. THE FRONT
WILL SAG BACK TO THE SOUTH TONIGHT WITH THE MODELS INDICATING A
NORTHWEST WIND SURGE 15-20 KNOTS AFTER MIDNIGHT.
THU-SUN...W/NW WINDS WILL PERSIST INTO LATE WEEK AND THROUGH THE
WEEKEND. PERIODS OF INCREASING WINDS UP TO NEAR/AROUND 20 KNOTS WILL
OCCUR AND CREATE ROUGHER BOATING CONDITIONS...ESPECIALLY OFFSHORE.
&&
.FIRE WEATHER...
TODAY...MIN RH VALUES SHOULD FALL TO AROUND 35 PERCENT ACROSS THE
INTERIOR FROM OSCEOLA NORTH.
THU-FRI...DRY AIRMASS OVER THE AREA WILL PRODUCE MIN RH VALUES
AROUND 30 TO 35 PERCENT OVER MUCH OF THE AREA EACH AFTERNOON.
HOWEVER WIND SPEEDS EXPECTED TO REMAIN JUST BELOW 15 MPH BOTH DAYS.
&&
.PRELIMINARY POINT TEMPS/POPS...
DAB 72 47 73 48 / 10 0 0 0
MCO 77 50 75 51 / 10 10 0 0
MLB 75 51 74 52 / 10 10 0 0
VRB 76 50 74 50 / 20 10 0 0
LEE 74 49 73 49 / 10 0 0 0
SFB 75 49 75 49 / 10 0 0 0
ORL 76 52 74 52 / 10 10 0 0
FPR 75 54 74 50 / 20 10 0 0
&&
.MLB WATCHES/WARNINGS/ADVISORIES...
FL...NONE.
AM...SMALL CRAFT ADVISORY UNTIL 9 AM THIS MORNING FOR WATERS FROM
FLAGLER BEACH TO VOLUSIA BREVARD COUNTY LINE 20 TO 60 NM
OFFSHORE-WATERS FROM VOLUSIA BREVARD COUNTY LINE TO SEBASTIAN
INLET 20 TO 60 NM OFFSHORE.
&&
$$
SHORT TERM/AVIATION...LASCODY
LONG TERM....WEITLICH
AREA FORECAST DISCUSSION
NWS DES MOINES IA
1156 PM CST TUE FEB 26 2013
.UPDATE...
INITIAL UPPER LOW IS LIFTING NORTHEAST THROUGH THE LOWER OHIO
VALLEY THIS EVENING WHILE THE SECOND UPPER LEVEL SYSTEM IS
PROGRESSING EAST THROUGH KANSAS. SEVERAL IMPULSES AREA MOVING
AROUND THE CYCLONIC FLOW AND ARE HELPING FLARE UP BANDS OF SNOW AS
THEY PASS THROUGH CENTRAL IA. ONE IMPULSE HAS SETTLED SOUTH INTO
NORTHERN MISSOURI WHILE THE NEXT IS NOW MOVING INTO NORTHEAST IOWA
OUT OF WISCONSIN WHILE ANOTHER IS BACK FARTHER EAST AND JUST
MOVING WEST FROM LAKE SUPERIOR. BETWEEN THE ENERGY...DRIER AIR HAS
FILTERED SOUTH AND NOW COVERS NEARLY THE NORTHWEST HALF OF THE
STATE AND HAS TEMPORARILY BROUGHT AN END TO THE SNOW OVER
NORTHWEST HEADLINE AREAS. IMPULSE MOVING INTO NORTHEAST IOWA WILL
HELP SHIFT ANOTHER BAND OF SNOW WESTWARD ACROSS THESE REGIONS.
LATEST SREF 100 MB DEPTH DENDRITIC GROWTH ZONE REMAINS LOCKED ON
TO THESE ENHANCED BANDS. TRENDS CONTINUE TO SUGGEST THE FOCUS FOR
DENDRITIC SNOW IS OVER CENTRAL IOWA THROUGH NOON WEDNESDAY.
ANOTHER 1 TO 3 INCHES LIKELY THROUGH THIS TIME THROUGH THE WARNED
AREA.
&&
.SHORT TERM /TONIGHT/...
WINTER STORM WILL PERSIST THROUGH WEDNESDAY MORNING AS LIGHT TO
MODERATE SNOW BANDING CONTINUES ON THE BACKSIDE OF THE SURFACE LOW
LOCATED IN SOUTHEAST MISSOURI. SURFACE LOW LOOKS TO SLOWLY MIGRATE
NORTHEAST FROM SOUTHEAST MISSOURI INTO CENTRAL ILLINOIS THIS EVENING
INTO TOMORROW MORNING. LEANED TOWARD A SREF/GFS/NAM12 BLEND FOR
TRENDS TONIGHT.
WEAK LIFT WITHIN THE DENDRITIC GROWTH ZONE CONTINUES THIS AFTERNOON
AND TONIGHT...AND EVEN PERSISTS INTO WEDNESDAY MORNING. HIGHER
CONFIDENCE WITH THE ADDITIONAL LIGHT SNOW AMOUNTS THROUGH WEDNESDAY
MORNING RESULTING IN ROUGHLY 1 TO 4 INCHES OF ADDITIONAL SNOW
THROUGH 12Z ACROSS THE WARNING AREA. THE SNOW BAND AXIS LOOKS TO
CONTINUE TO SLOWLY PIVOT COUNTERCLOCKWISE AROUND THE CENTRAL PORTION
OF THE FORECAST RESULTING IN SOME AREAS RECEIVING AN ELONGATED
PERIOD OF MODERATE TO BRIEF HEAVY SNOW THIS EVENING. WITH THE
CURRENT TRACK OF THE SURFACE LOW...NOT EXPECTING THIS BAND TO DRIFT
SOUTHEAST ALL THAT MUCH UNTIL EARLY WEDNESDAY MORNING.
GENERALLY EXPECTING A HALF TO POSSIBLY ONE INCH PER HOUR SNOWFALL
RATES THIS EVENING WITH THE WEAK LIFT IN THE DENDRITIC LAYER. SREF
100MB/50MB DENDRITE GROWTH ZONE PARAMETER DEPICTING 80-90 PERCENT
PROBABILITY OF DENDRITIC SNOW THROUGH TOMORROW AND MATCHES UP WELL
WITH PREVIOUSLY MENTION BAND PIVOTING ACROSS CENTRAL IOWA. BUFR
SOUNDINGS REMAIN DEEPLY SATURATED THROUGH WEDNESDAY MORNING...WITH
THE RAP SHOWING A MID LEVEL DRY LAYER ADVECTING INTO DSM TO ALO AND
MAY SEE A BRIEF BREAK IN THE SNOW MID TO LATE EVENING.
WINDS ATOP THE MIXED LAYER RANGE FROM 25 TO 30KTS THIS AFTERNOON AND
TONIGHT AND EXPECTING BLOWING SNOW IMPACTS TO CONTINUE AS WELL.
LEANED TOWARDS THE GFS/SREF QPF AMOUNTS TONIGHT AS NAM SEEMS TO HIGH
ACROSS THE EAST...ESPECIALLY WITH THE WEAKER FORCING.
.LONG TERM /WEDNESDAY THROUGH TUESDAY/...
WEAKER LIFT WILL PERSIST INTO WEDNESDAY WITH THE SPC SREF INDICATING
DEEP DENDRITIC GROWTH LAYER CONTINUING THROUGH CENTRAL IOWA. ALL
SOUNDINGS CONTINUE TO ALSO SHOW DEEP SATURATION THROUGH AT LEAST
MIDDAY TOMORROW AND ANTICIPATE THE LIGHT SNOW TO CONTINUE. HAVE
GONE WITH LIKELY TO CATEGORICAL POPS FOR MUCH OF THE AREA UNDER THE
CURRENT HEADLINE WITH THE SHARP CUTOFF ON THE NORTHERN SIDE OF THE
PCPN AREA PERSISTING. WINDS WILL REMAIN RATHER STRONG THROUGH THE
DAY WITH BRISK NORTHWEST FLOW PERSISTING WITH DECENT PRESSURE
GRADIENT. EVENTUALLY...THE FORCING WILL BE DIMINISHING WITH THE
SNOW TAPERING TO FLURRIES BY LATER IN THE DAY. CLOUDINESS IS
EXPECTED TO PERSIST AS WELL IN CYCLONIC FLOW ON BACKSIDE INTO
WEDNESDAY NIGHT WITH AN APPROACHING SHORTWAVE ON THURSDAY AND
THURSDAY NIGHT HELPING THE CLOUDINESS TO MAINTAIN. IN FACT...SOME
WEAK LIFT WITH THIS PASSING WAVE ON FRIDAY MAY HELP TO PRODUCE SOME
FLURRIES IN SOUTHERN IOWA DURING THE DAY.
UPPER RIDGING WILL SLIDE THROUGH THE REGION INTO THE WEEKEND WITH
QUIET WEATHER DURING THIS TIME. TEMPERATURES WILL REMAIN BELOW
NORMAL WITH WIDESPREAD SNOW PACK AND ONLY WEAK ADVECTION UNTIL
SUNDAY NIGHT. THIS WARM ADVECTION IS IN ADVANCE OF THE NEXT SYSTEM
WHICH WILL PASS THROUGH THE REGION ON MONDAY INTO TUESDAY IN BROAD
NORTHWEST FLOW. BOTH GFS AND EURO HAVE INDICATED SOME DECENT
FORCING AND ANTICIPATE PCPN DEVELOPING AND SLIDING ACROSS THE STATE
ON MONDAY INTO EARLY TUESDAY. SOUNDINGS WOULD INDICATE GENERALLY
SNOW DURING THIS TIME ACROSS THE STATE WITH LIGHT TO MODERATE
ACCUMULATIONS EXPECTED.
&&
.AVIATION...27/06Z
BANDS OF LIGHT TO MODERATE SNOW WILL CONTINUE OVERNIGHT ALONG WITH
MVFR TO IFR CIGS. THE CIGS SHOULD MOVE INTO THE KFOD/KMCW AREAS
OVERNIGHT AS WELL AFTER BEGINNING VFR. SNOW WILL GRADUALLY
DIMINISH AFTERNOON ON WEDNESDAY HOWEVER IFR TO MVFR CIGS LIKELY TO
CONTINUE THROUGH THE PERIOD. BREEZY NORTHERLY WINDS OVERNIGHT
WILL BECOME GUSTY AGAIN ON WEDNESDAY.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING UNTIL NOON CST WEDNESDAY FOR ADAIR-ADAMS-
APPANOOSE-BLACK HAWK-BOONE-CLARKE-DALLAS-DAVIS-DECATUR-GRUNDY-
HARDIN-JASPER-LUCAS-MADISON-MAHASKA-MARION-MARSHALL-MONROE-POLK-
POWESHIEK-RINGGOLD-STORY-TAMA-TAYLOR-UNION-WAPELLO-WARREN-WAYNE.
WINTER WEATHER ADVISORY UNTIL NOON CST WEDNESDAY FOR AUDUBON-
BREMER-BUTLER-CASS-FRANKLIN-GREENE-GUTHRIE-HAMILTON.
&&
$$
UPDATE...DONAVON
SHORT TERM...PODRAZIK
LONG TERM...COGIL
AVIATION...DONAVON
AREA FORECAST DISCUSSION
NWS DES MOINES IA
1101 PM CST TUE FEB 26 2013
.UPDATE...
INITIAL UPPER LOW IS LIFTING NORTHEAST THROUGH THE LOWER OHIO
VALLEY THIS EVENING WHILE THE SECOND UPPER LEVEL SYSTEM IS
PROGRESSING EAST THROUGH KANSAS. SEVERAL IMPULSES AREA MOVING
AROUND THE CYCLONIC FLOW AND ARE HELPING FLARE UP BANDS OF SNOW AS
THEY PASS THROUGH CENTRAL IA. ONE IMPULSE HAS SETTLED SOUTH INTO
NORTHERN MISSOURI WHILE THE NEXT IS NOW MOVING INTO NORTHEAST IOWA
OUT OF WISCONSIN WHILE ANOTHER IS BACK FARTHER EAST AND JUST
MOVING WEST FROM LAKE SUPERIOR. BETWEEN THE ENERGY...DRIER AIR HAS
FILTERED SOUTH AND NOW COVERS NEARLY THE NORTHWEST HALF OF THE
STATE AND HAS TEMPORARILY BROUGHT AN END TO THE SNOW OVER
NORTHWEST HEADLINE AREAS. IMPULSE MOVING INTO NORTHEAST IOWA WILL
HELP SHIFT ANOTHER BAND OF SNOW WESTWARD ACROSS THESE REGIONS.
LATEST SREF 100 MB DEPTH DENDRITIC GROWTH ZONE REMAINS LOCKED ON
TO THESE ENHANCED BANDS. TRENDS CONTINUE TO SUGGEST THE FOCUS FOR
DENDRITIC SNOW IS OVER CENTRAL IOWA THROUGH NOON WEDNESDAY.
ANOTHER 1 TO 3 INCHES LIKELY THROUGH THIS TIME THROUGH THE WARNED
AREA.
&&
.SHORT TERM /TONIGHT/...
WINTER STORM WILL PERSIST THROUGH WEDNESDAY MORNING AS LIGHT TO
MODERATE SNOW BANDING CONTINUES ON THE BACKSIDE OF THE SURFACE LOW
LOCATED IN SOUTHEAST MISSOURI. SURFACE LOW LOOKS TO SLOWLY MIGRATE
NORTHEAST FROM SOUTHEAST MISSOURI INTO CENTRAL ILLINOIS THIS EVENING
INTO TOMORROW MORNING. LEANED TOWARD A SREF/GFS/NAM12 BLEND FOR
TRENDS TONIGHT.
WEAK LIFT WITHIN THE DENDRITIC GROWTH ZONE CONTINUES THIS AFTERNOON
AND TONIGHT...AND EVEN PERSISTS INTO WEDNESDAY MORNING. HIGHER
CONFIDENCE WITH THE ADDITIONAL LIGHT SNOW AMOUNTS THROUGH WEDNESDAY
MORNING RESULTING IN ROUGHLY 1 TO 4 INCHES OF ADDITIONAL SNOW
THROUGH 12Z ACROSS THE WARNING AREA. THE SNOW BAND AXIS LOOKS TO
CONTINUE TO SLOWLY PIVOT COUNTERCLOCKWISE AROUND THE CENTRAL PORTION
OF THE FORECAST RESULTING IN SOME AREAS RECEIVING AN ELONGATED
PERIOD OF MODERATE TO BRIEF HEAVY SNOW THIS EVENING. WITH THE
CURRENT TRACK OF THE SURFACE LOW...NOT EXPECTING THIS BAND TO DRIFT
SOUTHEAST ALL THAT MUCH UNTIL EARLY WEDNESDAY MORNING.
GENERALLY EXPECTING A HALF TO POSSIBLY ONE INCH PER HOUR SNOWFALL
RATES THIS EVENING WITH THE WEAK LIFT IN THE DENDRITIC LAYER. SREF
100MB/50MB DENDRITE GROWTH ZONE PARAMETER DEPICTING 80-90 PERCENT
PROBABILITY OF DENDRITIC SNOW THROUGH TOMORROW AND MATCHES UP WELL
WITH PREVIOUSLY MENTION BAND PIVOTING ACROSS CENTRAL IOWA. BUFR
SOUNDINGS REMAIN DEEPLY SATURATED THROUGH WEDNESDAY MORNING...WITH
THE RAP SHOWING A MID LEVEL DRY LAYER ADVECTING INTO DSM TO ALO AND
MAY SEE A BRIEF BREAK IN THE SNOW MID TO LATE EVENING.
WINDS ATOP THE MIXED LAYER RANGE FROM 25 TO 30KTS THIS AFTERNOON AND
TONIGHT AND EXPECTING BLOWING SNOW IMPACTS TO CONTINUE AS WELL.
LEANED TOWARDS THE GFS/SREF QPF AMOUNTS TONIGHT AS NAM SEEMS TO HIGH
ACROSS THE EAST...ESPECIALLY WITH THE WEAKER FORCING.
.LONG TERM /WEDNESDAY THROUGH TUESDAY/...
WEAKER LIFT WILL PERSIST INTO WEDNESDAY WITH THE SPC SREF INDICATING
DEEP DENDRITIC GROWTH LAYER CONTINUING THROUGH CENTRAL IOWA. ALL
SOUNDINGS CONTINUE TO ALSO SHOW DEEP SATURATION THROUGH AT LEAST
MIDDAY TOMORROW AND ANTICIPATE THE LIGHT SNOW TO CONTINUE. HAVE
GONE WITH LIKELY TO CATEGORICAL POPS FOR MUCH OF THE AREA UNDER THE
CURRENT HEADLINE WITH THE SHARP CUTOFF ON THE NORTHERN SIDE OF THE
PCPN AREA PERSISTING. WINDS WILL REMAIN RATHER STRONG THROUGH THE
DAY WITH BRISK NORTHWEST FLOW PERSISTING WITH DECENT PRESSURE
GRADIENT. EVENTUALLY...THE FORCING WILL BE DIMINISHING WITH THE
SNOW TAPERING TO FLURRIES BY LATER IN THE DAY. CLOUDINESS IS
EXPECTED TO PERSIST AS WELL IN CYCLONIC FLOW ON BACKSIDE INTO
WEDNESDAY NIGHT WITH AN APPROACHING SHORTWAVE ON THURSDAY AND
THURSDAY NIGHT HELPING THE CLOUDINESS TO MAINTAIN. IN FACT...SOME
WEAK LIFT WITH THIS PASSING WAVE ON FRIDAY MAY HELP TO PRODUCE SOME
FLURRIES IN SOUTHERN IOWA DURING THE DAY.
UPPER RIDGING WILL SLIDE THROUGH THE REGION INTO THE WEEKEND WITH
QUIET WEATHER DURING THIS TIME. TEMPERATURES WILL REMAIN BELOW
NORMAL WITH WIDESPREAD SNOW PACK AND ONLY WEAK ADVECTION UNTIL
SUNDAY NIGHT. THIS WARM ADVECTION IS IN ADVANCE OF THE NEXT SYSTEM
WHICH WILL PASS THROUGH THE REGION ON MONDAY INTO TUESDAY IN BROAD
NORTHWEST FLOW. BOTH GFS AND EURO HAVE INDICATED SOME DECENT
FORCING AND ANTICIPATE PCPN DEVELOPING AND SLIDING ACROSS THE STATE
ON MONDAY INTO EARLY TUESDAY. SOUNDINGS WOULD INDICATE GENERALLY
SNOW DURING THIS TIME ACROSS THE STATE WITH LIGHT TO MODERATE
ACCUMULATIONS EXPECTED.
&&
.AVIATION...26/18Z
AREAS OF LIGHT TO MODERATE SNOW WILL CONTINUE TO IMPACT THE
KDSM/KOTM/KALO AREAS THROUGH TONIGHT. A MIX OF MVFR TO IFR STRATUS
WILL ACCOMPANY THE SNOW. KFOD AND KMCW WILL HAVE LESS SNOW THOUGH
PERIODS OF MVFR STRATUS OR LOWER ARE POSSIBLE AT TIMES. GUSTY
NORTHERLY WINDS WILL PREVAIL THROUGH WEDNESDAY
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING UNTIL NOON CST WEDNESDAY FOR ADAIR-ADAMS-
APPANOOSE-BLACK HAWK-BOONE-CLARKE-DALLAS-DAVIS-DECATUR-GRUNDY-
HARDIN-JASPER-LUCAS-MADISON-MAHASKA-MARION-MARSHALL-MONROE-POLK-
POWESHIEK-RINGGOLD-STORY-TAMA-TAYLOR-UNION-WAPELLO-WARREN-WAYNE.
WINTER WEATHER ADVISORY UNTIL NOON CST WEDNESDAY FOR AUDUBON-
BREMER-BUTLER-CASS-FRANKLIN-GREENE-GUTHRIE-HAMILTON.
&&
$$
UPDATE...DONAVON
SHORT TERM...PODRAZIK
LONG TERM...COGIL
AVIATION...DONAVON
AREA FORECAST DISCUSSION
NWS PADUCAH KY
831 PM CST THU FEB 28 2013
.MESOSCALE DISCUSSION...
ISSUED AT 830 PM CST THU FEB 28 2013
EARLY THIS EVENING...SOME MODEST POP CHANGES WERE MADE TO THE
FIRST PERIOD /TONIGHT/ AND FIRST HALF OF THE SECOND PERIOD /FRIDAY
MORNING/ TO HANDLE AN ENHANCEMENT OF LIFT/FORCING CAPABLE OF
GENERATING MEASURABLE /ALBEIT SMALL/ SNOW ACCUMULATION. THE VERY
HIGH RESOLUTION NAM-WRF FAMILY OF MODEL GUIDANCE...AS WELL AS THE
3KM HRRR GUIDANCE IRONICALLY DOES NOT GENERATE ANY MODEL
REFLECTIVITY IN THE AREA CURRENTLY COVERED BY PERSISTENT LIGHT
SNOWFALL OVER MISSOURI AND INTO SOUTHERN ILLINOIS. THE LATEST RUNS
OF THE SHORT RANGE ENSEMBLES /SREF/...THE CANADIAN /GEM/ AND TO
SOME DEGREE THE ECMWF PICK UP ON THE CHANNELED VORTICITY MOVING
ACROSS THE AREA. THE GOES WATER VAPOR...IR AND DIFFERENCE CHANNELS
SUGGEST THAT THE MAIN ZONE OF CHANNELED VORTICITY IS SWING ACROSS
NORTHEAST KANSAS AND INTO WESTERN AND SOUTHERN MO...WEDGED
BETWEEN THE RIDGE ALONG THE FRONT RANGE OF THE ROCKIES AND A BROAD
TROUGH OVER THE WFO PAH FORECAST AREA. THE SATELLITE IMAGERY
SUGGESTS THE ENHANCEMENT OF AN UPPER LEVEL LOW CIRCULATION NORTHEAST
OF QUINCY /KUIN/ IN WEST CENTRAL ILLINOIS. FURTHER TO THE
SOUTH...JUST SOUTH OF THE MISSOURI/KENTUCKY BORDER...THERE IS A
SLIGHT SHARPENING OF A BAROCLINIC LEAF...WITH AN INFLECTION POINT
MOVING NEAR JONESBORO ARKANSAS /KJBR/. THE GOES SOUNDER 7.0 AND 7.4
MICRON WATER VAPOR IMAGERY /SENSITIVE NEAR THE 700 AND 850 MB
LAYERS/ SHOW DEEPER MOISTURE FIXED OVER SOUTHEAST MISSOURI.
TAKING ALL OF THESE FEATURES INTO ACCOUNT...THE DEEPER AREA OF MOISTURE
NECESSARY FOR PRODUCTIVE AND MORE WIDESPREAD DENDRITIC ICE CRYSTAL
GROWTH WILL REMAIN BACK IN SOUTHEAST MISSOURI EARLY THIS EVENING.
THIS WILL LEAVE PART OF THE AREA IN A MIXED ZONE...WITH VERY LIGHT
RAIN AND SNOW POSSIBLE.
AS THE EVENING PROGRESSES...THE CYCLONIC CIRCULATION/LOW WILL
ROTATE DOWN TOWARD THE WFO PAH FORECAST AREA...ENHANCING THE
VORTICITY /AND ESSENTIALLY LIFT/ ACROSS THE LOCAL AREA. AT THE
SAME TIME...THE DEEPER MOISTURE WILL BE CHANNELED/PUSHED EASTWARD
THROUGH THE WFO PAH FORECAST AREA...SANDWICHED BETWEEN THE LOW TO
THE NORTH AND THE BAROCLINIC LEAF/SHEAR TO THE SOUTH. THE
COMBINATION OF THE INCREASE IN MOISTURE/LIFT/UPPER LEVEL FORCING
SHOULD CREATE A MORE EFFECTIVE ENVIRONMENT FOR SNOW PRODUCTION.
WITH COLD AIR ADVECTION STILL EXPECTED AT THE
SURFACE...TEMPERATURES SHOULD BE COLD ENOUGH TO SUPPORT AT LEAST
MINOR DEPOSITION OF SNOW ACROSS THE AREA...ESPECIALLY AFTER
MIDNIGHT AND THROUGH THE MORNING HOURS ON FRIDAY. FOR NOW...DO NOT
EXPECT A SNOW TOTAL BEYOND AN INCH...WITH THE GREATEST AMOUNTS
/0.7-0.9 OF AN INCH/ IN A NARROW BAND FROM CARBONDALE IL TO
HOPKINSVILLE KY. THE CURRENT SPECIAL WEATHER STATEMENT IN FORCE
HANDLES THIS SITUATION WELL...AS MOST OF THE SNOW SHOULD NOT BE
DEPOSITING DURING THE MORNING COMMUTE TIMES.
&&
.UPDATE...
ISSUED AT 536 PM CST THU FEB 28 2013
UPDATED THE AVIATION SECTION FOR THE 00Z TAF ISSUANCE.
&&
.SHORT TERM...(THIS EVENING THROUGH SATURDAY NIGHT)
ISSUED AT 258 PM CST THU FEB 28 2013
MAIN ISSUE FOR THE SHORT TERM WILL BE LIGHT SNOW POTENTIAL
TONIGHT. THE 12Z MODELS REMAIN CONSISTENT IN DEVELOPING A WEAK
500MB LOW ALONG THE KY/TN BORDER BY 12Z FRIDAY. THIS LOW DEVELOPS
OUT OF A BROAD TROUGH ALOFT THAT HAS BEEN IMPACTING THE AREA FOR A
FEW DAYS NOW.
THE WIND FIELDS ARE QUITE WEAK THROUGH THE ENTIRE COLUMN...WITH
LITTLE MORE THAN 20KTS AT ANY LEVEL. IT IS HARD TO GENERATE
SIGNIFICANT LIFT FOR PRECIPITATION WITHOUT SOME DECENT WINDS AT
SOME LEVEL. THE MODELS GENERATE ENOUGH LIFT TO SATURATE THE
COLUMN...BUT NOT TO GENERATE SIGNIFICANT PRECIPITATION.
THEREFORE...WOULD NOT EXPECT ANYTHING MORE THAN A VERY LIGHT SNOW
LATE TONIGHT AND FRIDAY.
SURFACE TEMPERATURES HAVE BEEN QUITE COOL FOR MUCH OF THE
WEEK...BUT IT HAS BEEN DIFFICULT TO GET FREEZING TEMPERATURES INTO
THE AREA. WITH ONLY MODEST NORTH WINDS EXPECTED
TONIGHT...SIGNIFICANT COLD ADVECTION IS NOT LIKELY. AS A RESULT SUB-
FREEZING AIR WILL LIKELY BE CONFINED TO OUR WEST AND NORTHWEST
AREAS. THIS WILL MAKE IT DIFFICULT FOR THE LIGHT SNOW THAT MAKES
IT TO THE GROUND TO ACTUALLY ACCUMULATE.
KEPT SNOW AMOUNTS AROUND A HALF INCH OR LESS...AND THAT MAY BE TOO
MUCH. CANNOT COMPLETELY RULE OUT SOME ISOLATED AREAS WITH UP TO AN
INCH...BUT TOO LITTLE CONFIDENCE TO PUT THAT MUCH IN THE GRIDS AT
THIS TIME. WOULD BE MOST CONCERNED FOR THIS TO HAPPEN OVER WEST
KENTUCKY FRIDAY TO THE NORTH OF THE EVENTUAL LOW...AND THIS IS
WHERE SURFACE TEMPERATURES ARE THE LEAST LIKELY TO GET DOWN TO
FREEZING. GIVEN THE LATE NIGHT/EARLY MORNING TIMING FOR MUCH OF
THE SNOW...WILL ISSUE A SPECIAL WEATHER STATEMENT TO MENTION THE
POSSIBILITY OF A FEW SLICK SPOTS ON BRIDGES AND UNTREATED/LESSER
TRAVELLED ROADWAYS.
GIVEN THE UNCERTAINTIES IN MEASURABLE SNOW...KEPT POPS AT MINIMAL
LIKELY LEVELS FOR THIS EVENT. SHOULD SEE THE SNOW TAPERING OFF
FROM NORTHWEST TO SOUTHEAST FRIDAY AND FRIDAY EVENING. THE
FORECAST WILL BE DRY SATURDAY AND SATURDAY NIGHT.
AS FOR TEMPERATURES WENT A BIT ABOVE GUIDANCE FOR LOWS TONIGHT AND
UNDERCUT CONSENSUS GUIDANCE FOR HIGHS ON FRIDAY. DRY AIR WILL
OVERSPREAD THE AREA FRIDAY NIGHT...SO DIURNAL RANGES WILL FINALLY
INCREASE...WITH COLD LOWS FRIDAY NIGHT AND SATURDAY NIGHT.
CONSENSUS LOOKS GOOD FOR THOSE LOWS AND HIGHS ON SATURDAY.
.LONG TERM...(SUNDAY THROUGH THURSDAY)
ISSUED AT 258 PM CST THU FEB 28 2013
SYNOPTIC PATTERN WILL REMAIN RATHER COLD AND UNSETTLED THROUGH MOST
OF THE LONG TERM. LONGWAVE TROUGH POSITION WILL REMAIN OVER THE
EASTERN STATES...WITH AT LEAST ONE POTENTIALLY SIGNIFICANT SHORTWAVE
TROUGH EXPECTED TO MOVE SOUTHEAST ACROSS OUR FORECAST AREA.
AS FAR AS THE DAILY DETAILS...
A NARROW RIDGE OF HIGH PRESSURE WILL MOVE EAST ACROSS THE
MISSISSIPPI VALLEY ON SUNDAY. THERE SHOULD BE PLENTY OF
SUNSHINE...BUT TEMPS WILL REMAIN UNSEASONABLY CHILLY EVEN WITH THE
SUN.
CLOUDS WILL INCREASE SUNDAY NIGHT AND MONDAY AHEAD OF A
SOUTHEASTWARD MOVING 500 MB SHORTWAVE. A NARROW RIBBON OF LIGHT
PRECIP IS INDICATED BY THE MODELS IN THE WARM ADVECTION ZONE AHEAD
OF THE SHORTWAVE. WILL INTRODUCE SLIGHT CHANCE POPS TO ACCOUNT FOR
THIS QPF. LOW LEVELS ARE FORECAST TO BE A LITTLE TOO WARM FOR PURE
SNOW...THOUGH A MIX OF RAIN AND SNOW IS POSSIBLE.
THE MORE SIGNIFICANT PRECIP TYPE ISSUES ARE MONDAY NIGHT AND TUESDAY
AS THE SHORTWAVE INTENSIFIES AND LIKELY CLOSES OFF AS IT DROPS
SOUTHEAST ACROSS THE CENTRAL STATES. MODEL DIFFERENCES ARE VERY
LARGE CONCERNING THE TRACK...INTENSITY...AND TIMING OF THE
SHORTWAVE. SURPRISINGLY...THERE IS NOT NEARLY AS MUCH DIFFERENCE IN
THE TRACK OF THE SURFACE LOW. THE SURFACE LOW IS FORECAST TO TRACK
EAST ACROSS NORTH MISSISSIPPI/NORTH ALABAMA MONDAY NIGHT BY THE 12Z
GFS AND ECMWF. THIS WOULD NORMALLY FAVOR SNOW...BUT THE ECMWF TRACK
OF THE 850 MB LOW IS QUITE A BIT FURTHER NORTH ACROSS THE LOWER OHIO
VALLEY...WHICH ALLOWS THE 850 MB ZERO ISOTHERM TO REACH THE OHIO
RIVER.
BOUNDARY LAYER TEMPS ARE OFTEN VERY MARGINAL FOR SNOW THIS TIME OF
YEAR...ESPECIALLY IN THE DAYTIME. FOR THAT REASON...THE TIMING OF
THE PRECIP MAY BE VERY IMPORTANT...WITH A BETTER CHANCE OF SNOW IF
THE HEAVIER PRECIP OCCURS LATER AT NIGHT OR EARLY IN THE MORNING.
POPS WILL BE KEPT IN THE CHANCE CATEGORY UNTIL MODELS COME INTO
BETTER AGREEMENT.
FOLLOWING THE PASSAGE OF THE SYSTEM...ANOTHER SURGE OF UNSEASONABLY
COLD AIR WILL OCCUR WEDNESDAY. THIS WILL BE QUICKLY FOLLOWED BY
SOUTHWEST RETURN FLOW OF MILDER AIR FOR THURSDAY...BUT TEMPS WILL
STILL STRUGGLE TO REACH NORMAL LEVELS FOR THIS TIME OF YEAR.
&&
.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 536 PM CST THU FEB 28 2013
MVFR CIGS SHOULD PREVAIL AT ALL SITES THROUGH THE PERIOD. MAY SEE
MVFR VSBYS AND POSSIBLY IFR CIGS AS PATCHES OF LIGHT SNOW PASS
ACROSS THE SITES THROUGH 15Z. RAIN MAY MIX WITH SNOW AFT 15Z AS
TEMPERATURES WARM INTO THE MID TO UPPER 30S. PRECIPITATION SHOULD
BE OVER AT ALL SITES BETWEEN 18-21Z. WINDS WILL GENERALLY STAY OUT OF THE
NORTHWEST AOB 10 KTS.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
MO...NONE.
IN...NONE.
KY...NONE.
&&
$$
MESOSCALE...SMITH
AVIATION...JP
AREA FORECAST DISCUSSION
NWS JACKSON KY
124 PM EST WED FEB 27 2013
.UPDATE...
ISSUED AT 124 PM EST WED FEB 27 2013
UPDATED TEMPS FOR THIS AFTERNOON AND EVENING BASED ON CURRENT OBS AND
THE HRRR MODEL. ALSO ADJUST PRECIP TYPE BASED ON THIS TONIGHT. THE
IMPACT ON THE OVERALL FORECAST IS NEGLIGIBLE.
UPDATE ISSUED AT 1007 AM EST WED FEB 27 2013
BASED ON RADAR TRENDS AND FORECAST SOUNDINGS...HAVE ADDED MORE RAIN
AND DRIZZLE TO THE FORECAST FOR TODAY...BUT ALL POPS ARE IN THE 20-30
PERCENT RANGE.
UPDATE ISSUED AT 627 AM EST WED FEB 27 2013
PRECIPITATION HAS TAPERED TO PRETTY MUCH JUST DRIZZLE AS THE COOLER
CLOUD TOPS HAVE EXITED. RUC/NAM BUFR SOUNDINGS CONTINUE TO SHOW A
LITTLE BIT OF MOISTURE ABOVE THE LOW LEVEL INVERSION SUPPORTING
DRIZZLE THROUGH MID MORNING. HOWEVER...SOME WEAK MID LEVEL SUBSIDENCE
WILL ESSENTIALLY TAKE ITS TOLL ON THIS SHALLOW MOISTURE BY LATE THIS
MORNING...LEAVING BEHIND GENERALLY OVERCAST SKIES. THE DRY CONDITIONS
ARE STILL EXPECTED TO PERSIST THROUGH THE AFTERNOON AND LIKELY INTO
THE EARLY EVENING HOURS. RAP/HRRR ALONG WITH SUPPORT FROM THE NAM HAS
RAIN SPREADING BACK INTO THE AREA TOWARDS 00Z TONIGHT. RAP/NAM STILL
STRONGLY SUPPORT MAINLY RAIN AT THE ONSET AS SURFACE TEMPERATURES
REMAIN TOO WARM FOR SNOW. HOWEVER...AS PRECIPITATION INTENSITY
INCREASES...WE SHOULD WETBULB DOWN CLOSER TO FREEZING FAIRLY QUICKLY
CHANGING ANY RAIN OVER TO SNOW BY LATE EVENING. ALL OF THIS IS STILL
IN LINE WITH THE LATEST FORECAST AND SEE NO REASON TO MAKE ANY
SIGNIFICANT CHANGES AT THIS TIME.
&&
.SHORT TERM...(TODAY THROUGH THURSDAY)
ISSUED AT 306 AM EST WED FEB 27 2013
AN UPPER LEVEL LOW WILL CONTINUE TO DRIFT EASTWARD ACROSS THE OHIO
RIVER VALLEY OVER THE NEXT 36 TO 48 HOURS. THIS WILL PROVIDE SEVERAL
ROUNDS OF UNSETTLED WEATHER THROUGH THE REMAINDER OF THE WEEK.
ONGOING LIGHT RAIN/DRIZZLE WILL CONTINUE TO PUSH NORTH AND EAST
THROUGH DAYBREAK. MODEL SOUNDINGS SHOW ICE ACTIVATION DWINDLING
TOWARDS DAYBREAK AS THE BETTER MOISTURE LIFTS TO THE NORTH AND EAST.
THIS WILL LIKELY PROVIDE A PERIOD OF DRIER WEATHER FROM THIS MORNING
INTO THEA AFTERNOON HOURS. HOWEVER...A VIGOROUS TROUGH WILL PUSH
SOUTH INTO EASTERN KENTUCKY LATE IN THE DAY AND TONIGHT...PRODUCING A
PERIOD OF RAIN...POSSIBLY MIXED WITH A LITTLE SNOW THIS EVENING. AS
TEMPERATURES QUICKLY COOL THIS EVENING...RAIN SHOULD QUICKLY
TRANSITION TO SNOW ON THE RIDGES WITH THE VALLEYS FOLLOWING A FEW
HOURS LATER. LOCATIONS ABOVE 1500 FEET WILL LIKELY BE ALL SNOW FROM
THE ONSET...AND WITH TEMPERATURES VERY COOL AT THESE HIGHER
ELEVATIONS...THE LARGEST SNOW ACCUMULATIONS WILL LIKELY FALL ABOVE
1500 FEET. UP TO 3 OR 4 INCHES MAY BE POSSIBLE ABOVE 2000 FEET.
HOWEVER...ALL RIDGES WILL LIKELY SEE SOME MINOR SNOW ACCUMULATIONS
(UNDER A HALF INCH) WITH THE VALLEYS STRUGGLING TO SEE ANY
ACCUMULATION. THE FAVORED UPSLOPE AREAS WILL BE FAVORED WITH THE MOST
SNOW POTENTIAL INTO THURSDAY. SURFACE TEMPERATURES WILL CLIMB INTO
THE MID TO UPPER 30S ON THURSDAY WITH SNOW ACCUMULATIONS NOT MUCH OF
A THREAT DURING THE DAY. IN FACT...WE MAY CHANGEOVER TO RAIN IN
SEVERAL AREAS.
.LONG TERM...(THURSDAY NIGHT THROUGH TUESDAY)
ISSUED AT 355 AM EST WED FEB 27 2013
THE MODELS CONTINUE IN FAIR AGREEMENT ALOFT FOR THE LONG TERM
PORTION OF THE FORECAST. THEY ALL TAKE A CLOSED LOW EAST OUT OF THE
REGION ON THURSDAY NIGHT LEAVING BEHIND JUST A GENERAL AREA OF LOW
HEIGHTS. PLENTY OF ENERGY WILL ALSO BE STUCK BACK HERE THROUGH THE
SOUTHERN PLAINS AND TENNESSEE VALLEY. THIS COLLECTION WILL START TO
CONSOLIDATE ON FRIDAY TO FORM A NEW SEMI-CLOSED LOW OVER THE
REGION...PRIMARILY IN RESPONSE TO A STRONG RIDGE BUILDING OVER THE
WEST. THE DEVELOPING LOW WILL SWIRL PLENTY OF SHORTWAVE
ENERGY...THOUGH GENERALLY WEAK...THROUGH THE AREA INTO SATURDAY
MAINTAINING UNSETTLED WEATHER. THE GFS FORMS ITS UPPER LOW A BIT
QUICKER THAN THE GEM AND ECMWF...MAINTAINING A STRONGER SOLUTION
THROUGH THE WEEKEND. GIVEN THE MODEL TRENDS WILL FAVOR A WEAKER
VERSION OF THE GFS...BUT DO LIKE ITS MORE PROGRESSIVE SOLUTION. THE
UPPER LOW WILL BECOME MORE OF A DEEP TROUGH THROUGH THE EASTERN HALF
OF THE NATION BY SUNDAY MORNING AND GET SHOVED EAST BY THE STRONG
WESTERN RIDGING. CONTINUING WITH THE CONSENSUS SOLUTION...HEIGHTS
WILL RISE OVER THE AREA LATER SUNDAY AND CERTAINLY INTO MONDAY AS
ENERGY TOPS THE RIDGE AND SLIDES BY JUST TO OUR EAST. HOWEVER...THE
PATTERN BECOMES MORE MUDDLED HEADING INTO THE MIDDLE OF NEXT WEEK AS
THE WESTERN RIDGE IS BASICALLY WIPED OUT BY ENERGY MOVING INTO THE
PLAINS AND IT SLINKS THROUGH THE AREA AS JUST A WEAK AND SHORT LIVED
RISE IN HEIGHTS MONDAY NIGHT. BY TUESDAY...THE ENERGY FROM THE RIDGE
KILLING WAVE WILL REACH THE MID SECTION OF THE NATION AND START TO
IMPACT THE OHIO VALLEY.
SENSIBLE WEATHER WILL FEATURE A CHILLY PATTERN WITH SEVERAL REINFORCING
SHOTS OF COLD AIR THROUGH THE WEEKEND. THE FIRST PART OF THE EXTENDED
WILL SEE SNOW SHOWERS ACCOMPANY THE COLDER AIR. HOWEVER...DEEP LAYER
MOISTURE AND UPPER LEVEL SUPPORT WILL BE LIMITED FOR MUCH OF THIS
TIME. ACCORDINGLY...THE ACCUMULATIONS ARE EXPECTED TO BE LIGHT AND
MAINLY CONFINED TO THE NIGHT TIME HOURS. THE HIGHER TERRAIN IN THE
FAR SOUTHEAST PARTS OF THE CWA WILL SEE THE BEST CHANCE FOR ANY
ACCUMULATION MEASURED IN MULTIPLE INCHES...WHILE THE REST OF THE AREA
WILL LIKELY END UP WITH LESS THAN AN INCH. THE BEST SHOT AT SEEING
LIGHT ACCUMULATIONS...EVEN IN THE VALLEYS...WILL BE THURSDAY NIGHT
GIVEN A COLDER AIR MASS. CERTAINLY ANY HEAVIER BURST OF SNOW OR
BANDING COULD LEAD TO BRIEF ACCUMULATIONS DURING THE DAYLIGHT
HOURS...BUT THESE ARE LIKELY TO BE THE EXCEPTION RATHER THAN THE
RULE THROUGHOUT THE PERIOD. THE REAL PROBLEM IS THE LACK OF A SOLID
SFC WAVE TO GEN UP THE PCPN THAT COULD TAKE ADVANTAGE OF THE COLD AIR
AND GIVE MORE THAN OCCASIONAL SKIFFS OF ACCUMULATION. LINGERING SNOW
SHOWERS THROUGH THE DAY SATURDAY AND INTO SUNDAY IN THE FAR SOUTHEAST
WILL KEEP THE POTENTIAL FOR SOME ADDITIONAL ACCUMULATIONS IN THE
FORECAST WITH THE HIGHER TERRAIN FAVORED...BUT CHILLY TEMPS EVEN
DURING THE DAY MAY ALSO ALLOW FOR LIGHT ACCUMULATIONS IN THE
VALLEYS THERE...TOO. THE BULK OF THE PCPN MOVES OUT BY SUNDAY WITH
JUST A SMALL CHANCE FOR A LEFT OVER SNOW SHOWER IN THE FAR EAST.
OTHERWISE...THE NEXT CHANCE OF SNOW OR RAIN WILL NOT BE UNTIL MONDAY
NIGHT AND CONTINUING INTO TUESDAY AS A SFC WAVE MOVES OUT OF THE
PLAINS.
THE CR GRID BLEND CAME IN DECENT ENOUGH...GIVEN THE PROMINENCE OF THE
GFS. DID FINE TUNE THE POP GRIDS TO ENHANCE THEM IN THE HIGHER
EASTERN TERRAIN AND DIMINISH THEM FURTHER WEST...AT LEAST THROUGH
SATURDAY. ONLY MADE MINOR TERRAIN BASED ADJUSTMENTS TO TEMPERATURES
THROUGH THE EXTENDED...MAINLY TO COOL THE RIDGES A BIT MORE DURING
THE DAYS.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1259 PM EST WED FEB 27 2013
MAINLY MVFR CONDITIONS WERE PRESENT AT TAF ISSUANCE...DUE TO
CEILINGS. THERE WAS ALSO DRIZZLE IN MANY AREAS. LATE TODAY RAIN
SHOULD DEVELOP OVER THE REGION FROM NW TO SE BETWEEN ABOUT 21Z AND
00Z. THE RAIN WILL MIX WITH SNOW FROM NW TO SE BETWEEN ABOUT 01Z AND
04Z...REDUCING VISIBILITY. VISIBILITY WILL VARY AS THE SNOW BEGINS...
BUT ON AVERAGE SHOULD STILL BE MVFR. THE PRECIPITATION SHOULD THEN
EASE SOMEWHAT AS IT CHANGES TO ALL SNOW FROM NW TO SE BETWEEN ABOUT
03Z AND 06Z. MAINLY LIGHT SNOW WILL THEN CONTINUE AT TIMES THROUGH
THE REMAINDER OF THE PERIOD. CEILINGS ARE EXPECTED TO LOWER TO IFR
FOR A PERIOD OF SEVERAL HOURS CENTERED AROUND DAWN...WITH MVFR
CONDITIONS OTHERWISE EXPECTED OVERNIGHT AND ON THURSDAY.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...HAL
SHORT TERM...KAS
LONG TERM...GREIF
AVIATION...HAL
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
340 PM EST WED FEB 27 2013
.SYNOPSIS...
AN UPPER LEVEL LOW WILL MOVE ACROSS THE AREA OVERNIGHT AND PUSH
INTO THE NORTHEAST FOR THE END OF THE WEEK. AS THE LOW SHIFTS EAST
OF THE REGION...COLDER AIR WILL FILTER INTO THE AREA TONIGHT AND
ALLOW FOR A MIX OF RAIN AND SNOW SHOWERS TO CHANGE OVER TO MOSTLY
SNOW SHOWERS INTO FRIDAY.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
THE LATEST RAP MID-LEVEL ANALYSIS INDICATES A RATHER ELONGATED
CLOSED UPPER LOW THAT STRETCHES ACROSS THE SOUTHERN GREAT LAKES
AND OHIO VALLEY. AT THE SURFACE...A 999MB LOW IS CENTERED ACROSS
SOUTHERN MICHIGAN WITH ANOTHER LOW DEVELOPING AS IT MOVES
NORTHWARD ACROSS NEW JERSEY. THE LOW IN MICHIGAN IS DRIVING A
SOUTHWESTERLY FLOW ACROSS THE AREA THIS TODAY. SOUNDINGS INDICATE A
SFC-900MB MELTING LAYER STRONG ENOUGH TO ALLOW FOR PRECIP SOUTH
AND WEST OF PITTSBURGH TO BE ALL RAIN. 1000-700MB 2840M THICKNESS
LINE ALSO SEEMS TO COINCIDE FAIRLY WELL WITH RAIN/SNOW LINE
NORTHEAST OF PITTSBURGH.
THIS EVENING...THE BROAD UPPER LOW WILL SLOWLY MEANDER EASTWARD
ACROSS THE OHIO VALLEY...WITH THE NEXT VORT LOBE SWINGING AROUND
ITS BASE. WRF-ARW 1KM SIMULATED REFLECTIVITY DEPICTS MORE
CONVECTIVE SHOWERS EARLY THIS EVENING...SO HAVE GONE WITH
ISOLATED/SCATTERED INCREASING TO MORE NUMEROUS AS THE UPPER LOW
APPROACHES FROM THE WEST. DESPITE COLDER AIR ADVECTING IN WITH
THE COLD POOL ALOFT AND ASSOCIATED UPPER LOW...GFS/NAM SOUNDINGS
CONTINUE TO INDICATE PRECIPITATION WILL FALL INITIALLY AS RAIN
WITH A SUFFICIENT SFC-900MB MELTING LAYER REMAINING IN PLACE.
THUS...FORECAST BEINGS WITH MOSTLY RAIN...EXCEPT FOR SOME RAIN-SNOW
CLOSER TO 1000-700MB CRITICAL THICKNESS ACROSS THE NORTH AND WITH
THE LACK OF A PRONOUNCED MELTING LAYER ACROSS THE RIDGES.
OVERNIGHT...GFS/NAM AGREE THAT THE UPPER LOW WILL CROSS THE AREA AS
IT SHIFTS FROM WESTERN OHIO INTO WESTERN NY. WEAK CAA AND COOLING
SFC-900MB LAYER WILL ALLOW FOR ENTIRE COLUMN TO DROP BELOW
FREEZING AND PRECIPITATION TO CHANGE OVER TO ALL SNOW SHOWERS
TONIGHT. ACCUMULATIONS WILL BE AN INCH OR LESS FOR SOUTHWEST
PA...EASTERN OHIO...AND NORTHERN WV WITH 1 TO 2 INCHES POSSIBLE
TONIGHT ACROSS THE ALLEGHENY FRONT/LAUREL HIGHLANDS AND I-80
CORRIDOR. TEMPS TONIGHT ARE FAIRLY CLOSE TO A MAV/MET BLEND...WITH
LOWS RANGING FROM THE MID 20S ACROSS THE EASTERN RIDGES TO THE
LOWER 30S ELSEWHERE.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY/...
A MODEL CONSENSUS INDICATES THAT THE UPPER LOW WILL SLOWLY MEANDER
EASTWARD INTO NEW ENGLAND THURSDAY AND FRIDAY...LEAVING THE UPPER
OHIO VALLEY IN A MOIST...NORTHWESTERLY FLOW OFF OF THE GREAT
LAKES.
THE LOW-LEVEL FLOW WILL BE CLOSE TO ZONAL MUCH OF THE DAY THURSDAY
AS A SERIES OF VORT LOBES ROTATES AROUND THE UPPER LOW AND INTO
THE AREA. WITH SFC TEMPS WARMING TO THE MID TO UPPER 30S ACROSS
THE LOWLANDS...ANTICIPATE LITTLE ACCUMULATION DURING DAYLIGHT
HOURS ACROSS THE LOWLANDS. WITH SOME UPSLOPING AND TEMPS IN THE
LOWER 30S...1 TO 2 INCHES WILL BE POSSIBLE ACROSS THE HIGHER
ELEVATIONS.
VORT ENERGY WILL SLIDE EAST OF THE UPPER OHIO VALLEY THURSDAY
NIGHT INTO FRIDAY. DURING THIS TIME...THE LOW-LEVEL FLOW WILL
VEER TO MORE NORTH-NORTHWESTERLY...ALLOWING FOR A MOISTURE FETCH
OFF OF LAKE HURON WITH MOISTURE LACKING FROM A PARTIALLY FROZEN
LAKE ERIE. ONE LIMITING FACTOR DESPITE THE NNWRLY FLOW WILL BE
THAT THE AIR MASS WILL NOT BE QUITE COLD ENOUGH TO SUPPORT LAKE
EFFECT. THUS...ANTICIPATE LITTLE MORE THAN SCATTERED SNOW SHOWERS
THROUGH THIS PERIOD WITH AROUND AN INCH FOR THE LOWLANDS AND AN
ADDITIONAL 1 TO 2 FOR THE RIDGES. TEMPS THROUGH THIS PERIOD WILL
BE AROUND 5 DEGREES BELOW NORMAL WITH THE NORTHERLY COMPONENT
CONTINUING TO PULL COOLER...CANADIAN AIR INTO THE AREA.
&&
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
ECMWF AND GFS INDICATE CONTD MAINTENANCE OF THE ERN NORTH
AMERICAN TROF VIA SHRTWV ENERGY THRU THE LONG TERM PD. THE
EXTENDED FORECAST THUS CONTINUES TO FEATURE SUB AVERAGE TEMPS AND
NR CLIMO/CHC POPS UNTIL THE TROF AXIS SHIFT SUFFICIENTLY
EWD...PROBABLY BY SATURDAY.
SHRTWV RIDGE IN ADVN OF MIDWRN LOW IS CURRENTLY PROGGED TO
SUPPRESS PRECIP PROBABILITIES...UNTIL THE LOW INITIATES PCPN LTR
ON TUE. CONFIDENCE IN THAT PORTION OF THE FORECAST IS MINIMAL
GIVEN PROJECTIONS OF A CUTOFF SYSTEM WITH QUESTIONS OF MAGNITUDE
AND PLACEMENT OF THE LOW CENTERS.
&&
.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
GENL MVFR WITH STRATOCU CIGS WITH REDEVELOPMENT OF RAIN AND SNOW
SHOWERS CAN BE EXPECTED FOR THE TAF PD AS UPR LOW PRES DRIFTS ACRS
THE REGION.
.OUTLOOK.../WEDNESDAY NIGHT THROUGH SUNDAY/...
RESTRICTIONS ARE LIKLEY WITH CIGS AND -SHSN INTO THE WEEKEND. A
RETURN TO WIDESPREAD VFR CONDITIONS MAY NOT OCCUR UNTIL SUNDAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
SYNOPSIS...WOODRUM
NEAR TERM...WOODRUM
SHORT TERM...WOODRUM
LONG TERM...15
AVIATION...15
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
1259 PM EST WED FEB 27 2013
.SYNOPSIS...
AN UPPER LEVEL LOW WILL MOVE ACROSS THE AREA TODAY AND PUSH INTO THE
NORTHEAST FOR THE END OF THE WEEK. AS THE LOW SHIFTS EAST OF THE
REGION...COLDER AIR WILL FILTER INTO THE AREA TONIGHT AND ALLOW
FOR A MIX OF RAIN AND SNOW SHOWERS TODAY TO CHANGE OVER TO
MOSTLY SNOW SHOWERS TONIGHT INTO FRIDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
AN EARLY AFTERNOON ENHANCED SHORT TERM FORECAST UPDATE HAS BEEN
ISSUED TO BEGIN MIXING IN SNOW WITH RAIN SHOWERS 1-2 HOURS EARLIER
ACROSS THE AREA THIS EVENING. THE REST OF THE PREVIOUS DISCUSSION
REMAINS THE SAME.
THE LATEST RAP MID-LEVEL ANALYSIS INDICATES A RATHER ELONGATED
CLOSED UPPER LOW THAT STRETCHES ACROSS THE SOUTHERN GREAT LAKES
REGION. 500MB VORT ENERGY ALONG WITH 700MB OMEGA INDICATE THAT AN
AREA OF LIFT SPAWNING MORE WIDESPREAD RAIN/SNOW THIS MORNING
NORTHEAST OF PITTSBURGH HAS SHIFTED INTO NORTH-CENTRAL PA AND NEW
YORK. NVA IN ITS WAKE IS ALLOWING FOR A BREAK IN PRECIPITATION
ACROSS MOST OF THE AREA. AT THE SURFACE...A 999MB LOW IS CENTERED
ACROSS SOUTHERN MICHIGAN WITH ANOTHER LOW DEVELOPING AS IT MOVES
NORTHWARD ACROSS NEW JERSEY. THE LOW IN MICHIGAN IS DRIVING A
SOUTHWESTERLY FLOW ACROSS THE AREA THIS TODAY. THE 12Z KPIT
SOUNDING INDICATES A SFC-900MB MELTING LAYER STRONG ENOUGH TO
ALLOW FOR MOSTLY PRECIP SOUTH AND WEST OF PITTSBURGH TO BE ALL
RAIN. 1000-700MB 2840M THICKNESS LINE ALSO SEEMS TO COINCIDE
FAIRLY WELL WITH RAIN/SNOW LINE NORTHEAST OF PITTSBURGH.
THIS AFTERNOON...THE BROAD UPPER LOW WILL SLOWLY MEANDER EASTWARD
ACROSS THE OHIO VALLEY...WITH THE NEXT VORT LOBE SWINGING AROUND
ITS BASE THIS EVENING. WRF-ARW 1KM SIMULATED REFLECTIVITY DEPICTS
MORE CONVECTIVE SHOWERS THIS AFTERNOON AND EARLY EVENING...SO HAVE
GONE WITH ISOLATED/SCATTERED INCREASING TO MORE NUMEROUS AS THE
UPPER LOW APPROACHES FROM THE WEST. 850MB TEMPS WILL COOL FROM -1
TO -2C TO -3 TO -4C BY THIS EVENING. DESPITE COLDER AIR ADVECTING
IN WITH THE COLD POOL ALOFT AND ASSOCIATED UPPER LOW...GFS/NAM
SOUNDINGS CONTINUE TO INDICATE PRECIPITATION WILL FALL AS MOSTLY
RAIN TODAY WITH A SUFFICIENT SFC-900MB MELTING LAYER REMAINING IN
PLACE. THUS...HAVE GONE WITH MOSTLY RAIN IN THE FORECAST
TODAY...EXCEPT FOR SOME RAIN-SNOW CLOSER TO 1000-700MB CRITICAL
THICKNESS ACROSS THE NORTH AND WITH THE LACK OF A PRONOUNCED
MELTING LAYER ACROSS THE RIDGES. SOUTHWESTERLY FLOW WILL ALLOW
TEMPS TO WARM A FEW DEGREES THIS AFTERNOON...WITH HIGHS CLOSE TO
LAMP GUIDANCE...RANGING FROM THE MID 30S ACROSS THE EASTERN RIDGES
TO THE MID 40S SOUTH AND WEST OF PITTSBURGH.
TONIGHT...GFS/NAM AGREE THAT THE UPPER LOW WILL CROSS THE AREA AS
IT SHIFTS FROM WESTERN OHIO INTO WESTERN NY. WEAK CAA AND COOLING
SFC-900MB LAYER WILL ALLOW FOR ENTIRE COLUMN TO DROP BELOW
FREEZING AND PRECIPITATION TO CHANGE OVER TO ALL SNOW SHOWERS
TONIGHT. ACCUMULATIONS WILL BE AN INCH OR LESS FOR SOUTHWEST
PA...EASTERN OHIO...AND NORTHERN WV WITH 1 TO 2 INCHES POSSIBLE
TONIGHT ACROSS THE ALLEGHENY FRONT/LAUREL HIGHLANDS AND I-80
CORRIDOR. TEMPS TONIGHT ARE FAIRLY CLOSE TO A MAV/MET BLEND...WITH
LOWS RANGING FROM THE MID 20S ACROSS THE EASTERN RIDGES TO THE
LOWER 30S ELSEWHERE.
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY/...
MATURE/STACKED AND COLD LOW PRES WILL WOBBLE ACROSS THE REGION
THROUGH THURSDAY...AND DIG OFF THE COAST BY FRIDAY ACCORDING TO
THE LATEST MODEL SOLNS. SCT TO NMRS SHSN WL THUS CONT TO PLAGUE THE
REGION FOR THE SHORT TERM PD...WITH UPSLOPE COMPONENT OF WIND
ENHANCING SN POTENTIAL IN THE RIDGES.
OVERALL ACCUMULATION POTENTIAL WL BE RETARDED OVR AREAS WHERE
DAYTIME TEMPS RISE ABOVE FREEZING...SO HEADLINE POTENTIAL IS
LIMITED. THE EXCEPTION MAY BE FOR THE RIDGES WHERE PROLONGED SHSN
MAY REQUIRE A COUPLE-DAY ADVISORY. FOR NOW...WL MENTION IN THE
HAZARDOUS WEATHER OUTLOOK AND TASK FUTURE SHIFTS TO MONITOR.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
ECMWF AND GFS INDICATE CONTD MAINTENANCE OF THE ERN NORTH
AMERICAN TROF VIA SHRTWV ENERGY THRU THE LONG TERM PD. THE
EXTENDED FORECAST THUS CONTINUES TO FEATURE SUB AVERAGE TEMPS AND
NR CLIMO/CHC POPS UNTIL THE TROF AXIS SHIFT SUFFICIENTLY
EWD...PROBABLY BY SUNDAY.
SHRTWV RIDGE IN ADVN OF MIDWRN LOW IS CURRENTLY PROGGED TO
SUPPRESS PRECIP PROBABILITIES...UNTIL THE LOW INITIATES PCPN LTR
ON TUE. CONFIDENCE IN THAT PORTION OF THE FORECAST IS MINIMAL
GIVEN PROJECTIONS OF A CUTOFF SYSTEM WITH QUESTIONS OF MAGNITUDE
AND PLACEMENT OF THE LOW CENTERS.
&&
.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
GENL MVFR WITH STRATOCU CIGS WITH REDEVELOPMENT OF RAIN AND SNOW
SHOWERS CAN BE EXPECTED FOR THE TAF PD AS UPR LOW PRES DRIFTS ACRS
THE REGION.
.OUTLOOK.../WEDNESDAY NIGHT THROUGH SUNDAY/...
RESTRICTIONS ARE LIKLEY WITH CIGS AND -SHSN INTO THE WEEKEND. A
RETURN TO WIDESPREAD VFR CONDITIONS MAY NOT OCCUR UNTIL LATE
SUNDAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
SYNOPSIS...WOODRUM
NEAR TERM...WOODRUM
AVIATION...15
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
1114 AM EST WED FEB 27 2013
.SYNOPSIS...
AN UPPER LEVEL LOW WILL MOVE ACROSS THE AREA TODAY AND PUSH INTO THE
NORTHEAST FOR THE END OF THE WEEK. AS THE LOW SHIFTS EAST OF THE
AREA...COLDER AIR WILL FILTER INTO THE AREA TONIGHT AND ALLOW FOR A
MIX OF RAIN AND SNOW SHOWERS TODAY TO CHANGE OVER TO MOSTLY SNOW
SHOWERS TONIGHT INTO FRIDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
AN ENHANCED SHORT TERM FORECAST UPDATE HAS BEEN ISSUED TO ACCOUNT
FOR THE LATEST TRENDS IN TEMP AND RADAR AS A MIX OF RAIN SNOW
DIMINISHES NORTHEAST OF PITTSBURGH.
THE LATEST RAP MID-LEVEL ANALYSIS INDICATES A RATHER ELONGATED
CLOSED UPPER LOW THAT STRETCHES ACROSS THE SOUTHERN GREAT LAKES
REGION. 500MB VORT ENERGY ALONG WITH 700MB OMEGA INDICATE THAT AN
AREA OF LIFT SPAWNING MORE WIDESPREAD RAIN/SNOW THIS MORNING
NORTHEAST OF PITTSBURGH IS SHIFTING INTO NORTH-CENTRAL PA AND NEW
YORK. NVA IN ITS WAKE IS ALLOWING FOR A BREAK IN PRECIPITATION
MOVING FROM EASTERN OHIO INTO WESTERN PA. AT THE SURFACE...A 999MB
LOW IS CENTERED ACROSS SOUTHERN MICHIGAN WITH ANOTHER LOW
DEVELOPING AS IT MOVES NORTHWARD ACROSS NEW JERSEY. THE LOW IN
MICHIGAN IS DRIVING A SOUTHWESTERLY FLOW ACROSS THE AREA THIS
TODAY. THE 12Z KPIT SOUNDING INDICATES A SFC-900MB MELTING LAYER
STRONG ENOUGH TO ALLOW FOR MOSTLY PRECIP SOUTH AND WEST OF
PITTSBURGH TO BE ALL RAIN. 1000-700MB 2840M THICKNESS LINE ALSO
SEEMS TO COINCIDE FAIRLY WELL WITH RAIN CHANGING TO SNOW NORTHEAST
OF PITTSBURGH.
TODAY...THE BROAD UPPER LOW WILL SLOWLY MEANDER EASTWARD ACROSS THE
OHIO VALLEY...WITH THE NEXT VORT LOBE SWINGING AROUND ITS BASE THIS
EVENING. WRF-ARW 1KM SIMULATED REFLECTIVITY DEPICTS MORE CONVECTIVE
SHOWERS THIS AFTERNOON AND EARLY EVENING...SO HAVE GONE WITH
ISOLATED/SCATTERED INCREASING TO MORE NUMEROUS AS THE UPPER LOW
APPROACHES FROM THE WEST. 850MB TEMPS WILL COOL FROM -1 TO -2C TO
-3 TO -4C BY THIS EVENING. DESPITE COLDER AIR ADVECTING IN WITH
THE COLD POOL ALOFT AND ASSOCIATED UPPER LOW...GFS/NAM SOUNDINGS
CONTINUE TO INDICATE PRECIPITATION WILL FALL AS MOSTLY RAIN TODAY
WITH A SUFFICIENT SFC-900MB MELTING LAYER REMAINING IN PLACE.
THUS...HAVE GONE WITH MOSTLY RAIN IN THE FORECAST TODAY...EXCEPT
FOR SOME RAIN-SNOW CLOSER TO 1000-700MB CRITICAL THICKNESS ACROSS
THE NORTH AND WITH THE LACK OF A PRONOUNCED MELTING LAYER ACROSS
THE RIDGES. SOUTHWESTERLY FLOW WILL ALLOW TEMPS TO WARM A FEW
DEGREES THIS AFTERNOON...WITH HIGHS CLOSE TO LAMP
GUIDANCE...RANGING FROM THE MID 30S ACROSS THE EASTERN RIDGES TO
THE MID 40S SOUTH AND WEST OF PITTSBURGH.
TONIGHT... GFS/NAM AGREE THAT THE UPPER LOW WILL CROSS THE AREA AS
IT SHIFTS FROM WESTERN OHIO INTO WESTERN NY. WEAK CAA AND COOLING
SFC-900MB LAYER WILL ALLOW FOR ENTIRE COLUMN TO DROP BELOW
FREEZING AND PRECIPITATION TO CHANGE OVER TO ALL SNOW SHOWERS
TONIGHT. ACCUMULATIONS WILL BE AN INCH OR LESS FOR SOUTHWEST
PA...EASTERN OHIO...AND NORTHERN WV WITH 1 TO 2 INCHES POSSIBLE
TONIGHT ACROSS THE ALLEGHENY FRONT/LAUREL HIGHLANDS AND I-80
CORRIDOR. TEMPS TONIGHT ARE FAIRLY CLOSE TO A MAV/MET
BLEND...WITH LOWS RANGING FROM THE MID 20S ACROSS THE EASTERN
RIDGES TO THE LOWER 30S ELSEWHERE.
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY/...
MATURE/STACKED AND COLD LOW PRES WILL WOBBLE ACROSS THE REGION
THROUGH THURSDAY...AND DIG OFF THE COAST BY FRIDAY ACCORDING TO
THE LATEST MODEL SOLNS. SCT TO NMRS SHSN WL THUS CONT TO PLAGUE THE
REGION FOR THE SHORT TERM PD...WITH UPSLOPE COMPONENT OF WIND
ENHANCING SN POTENTIAL IN THE RIDGES.
OVERALL ACCUMULATION POTENTIAL WL BE RETARDED OVR AREAS WHERE
DAYTIME TEMPS RISE ABOVE FREEZING...SO HEADLINE POTENTIAL IS
LIMITED. THE EXCEPTION MAY BE FOR THE RIDGES WHERE PROLONGED SHSN
MAY REQUIRE A COUPLE-DAY ADVISORY. FOR NOW...WL MENTION IN THE
HAZARDOUS WEATHER OUTLOOK AND TASK FUTURE SHIFTS TO MONITOR.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
ECMWF AND GFS CONT TO INDICATE DEVELOPMENT OF AN ERN NORTH AMERICAN
TROF FOR THE LONG TERM PD. THE EXTENDED FORECAST THUS CONTINUES
TO FEATURE SUB AVERAGE TEMPS AND NR CLIMO. CHC POPS DEPENDENT ON
SPPRTG SHRTWV ENERGY FOR THE INTIAL PDS.
SHRTWV RIDGE IN ADVN OF MIDWRN LOW SHOULD REDUCE THOSE POPS BY
MONDAY...BUT THAT REPRIEVE LOOKS TO BE BRIEF AS PCPN FM THAT SYSTEM
IS CURRENTLY TIMED FOR A TUE INITIATION OVR THE UPR OH VALLEY.
&&
.AVIATION /16Z WEDNESDAY THROUGH SUNDAY/...
GENL MVFR WITH STRATOCU CIGS AND PERIODIC RAIN AND SNOW SHOWERS
CAN BE EXPECTED FOR THE TAF PD AS UPR LOW PRES DRIFTS ACRS THE
REGION.
.OUTLOOK.../WEDNESDAY NIGHT THROUGH SUNDAY/...
RESTRICTIONS ARE POSSIBLE IN RAIN OR SNOW SHOWERS THROUGH FRIDAY.
BEST CHANCE FOR A RETURN TO WIDESPREAD VFR CONDITIONS MAY NOT ARRIVE
UNTIL LATE SAT/SUN.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
SYNOPSIS...WOODRUM
NEAR TERM...WOODRUM
AVIATION...15
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
429 PM EST WED FEB 27 2013
.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 426 PM EST WED FEB 27 2013
WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW A BROAD MID LEVEL LOW
CIRCULATION OVER THE GREAT LAKES/OHIO VALLEY. AT THE SFC...A
WEAKENING LOW PRES CENTER WAS LOCATED NEAR FLINT. SYSTEM ENDED UP
SLIGHTLY FARTHER N THAN EXPECTED YESTERDAY...AND THUS THE ASSOCIATED
WEAKENING SNOW SHIELD WAS ABLE TO SPREAD FARTHER N AND W INTO UPPER
MI TODAY...AIDED BY A SHORTWAVE THAT PIVOTED AROUND THE LARGE MID
LEVEL LOW CIRCULATION. THE NW EDGE OF THE -SN HAS SPREAD TO ABOUT A
BIG BAY/CHAMPION/CRYSTAL FALLS LINE. SNOW ACCUMULATIONS HAVE
GENERALLY BEEN 1 INCH OR LESS THOUGH SOME 2-3 INCH AMOUNTS WERE
OBSERVED ACROSS MENOMINEE/DELTA/SRN SCHOOLCRAFT COUNTIES. SINCE THE
WEAKENING SHORTWAVE AND ASSOCIATED DEEP LAYER FORCING ASSOCIATED
WITH THE HEAVIER SNOW HAS ROTATED TO THE SW...-SN HAS BEEN
DIMINISHING IN AREAL COVERAGE FROM LATE MORNING THRU THE AFTN. AS
EXPECTED...THERE HAS NOT BEEN ANY EVIDENCE OF LES TODAY DESPITE
CYCLONIC NE FLOW AS AIR MASS HAS BEEN TOO WARM. IN FACT...ON VIS
SATELLITE IMAGERY...HIGH CLOUDS ARE AT TIMES THIN ENOUGH TO REVEAL
LITTLE IF ANY LAKE EFFECT CLOUDS OVER LAKE SUPERIOR. THE SNOW THAT
HAS RECENTLY INCREASED INTO NCNTRL UPPER MI APPEARS MOSTLY RELATED
TO A LONG ARC OF ISENTROPIC ASCENT EXTENDING W FROM NEW ENGLAND...
BUT IT CERTAINLY LOOKS LIKE THERE MAY NOW BE A LAKE COMPONENT TO
THIS HEAVIER SNOW THAT HAS DEVELOPED.
IN THE SHORT TERM...FOCUS SHIFTS FROM REMNANT -SN ASSOCIATED WITH
SLOWLY DEPARTING GREAT LAKES/OHIO VALLEY MID LEVEL LOW TO POTENTIAL
OF LES OFF LAKE SUPERIOR. WITH NO ADDITIONAL SHORTWAVES EVIDENT
PIVOTING TOWARD UPPER MI AND WITH MODELS INDICATING INCREASING DEEP
LAYER QVECTOR CONVERGENCE WITH TIME...EXPECT LINGERING AREAS OF -SN
OVER ROUGHLY THE E HALF OF UPPER MI TO CONTINUE TO DIMINISH TONIGHT.
ANY ADDITIONAL SNOW ACCUMULATION WILL BE LESS THAN 1 INCH.
ATTENTION THEN TURNS TO POTENTIAL LES OFF LAKE SUPERIOR. HIGHER RES
MODEL GUIDANCE CONTINUES TO POINT TOWARD LES/UPSLOPE ENHANCED SNOW
TONIGHT. ALTHOUGH DEEPER MOISTURE/SATURATION AND SYNOPTIC -SN IS
SPREADING OUT OVER ERN LAKE SUPERIOR...HAVE DOUBTS ON THE INSISTENCE
OF HIGH RES GUIDANCE TO OUTPUT IN WHAT SOME CASES ARE SIGNIFICANT
PCPN TOTALS TONIGHT (REGIONAL GEM SHOWS AROUND 0.5 INCHES OF PCPN
TONIGHT OVER THE HIGHER TERRAIN OF MARQUETTE COUNTY...LOCAL HIGH
RESWRF 0.3-0.4...06Z NAM SHOWED UPWARDS OF 1 INCH BUT 12Z NAM AT
LEAST TRENDED DOWN TO WHAT SHOULD BE A MORE REASONABLE 0.2-0.3).
850MB TEMPS OF ONLY -6 TO -9C ACROSS LAKE SUPERIOR WILL NOT BE
SUFFICIENT FOR LES. SO...ONCE THE ISENTROPIC ASCENT CURRENTLY AIDING
THE SNOW INTO NCNTRL UPPER MI FALLS APART TONIGHT...EXPECT THE SNOW
TO DIMINISH SIGNIFICANTLY. WILL THUS CARRY HIGH POPS INTO NCNTRL
UPPER MI THIS EVENING...THEN DIMINISH PCPN TO JUST SCT -SHSN
OVERNIGHT. EXPECT A FEW INCHES OF SNOW ACCUMULATION THRU THE EVENING
ACROSS THE HIGHER TERRAIN OF THE NCNTRL (MARQUETTE COUNTY IN
PARTICULAR). IF THE ONGOING SNOW SHOWS SIGNS OF PERSISTENCE AND
LITTLE MOVEMENT (HEAVIEST SNOW IS CURRENTLY OCCURRING FROM
MARQUETTE/HARVEY WSW TO ISHPEMING/GWINN) WILL LIKELY NEED TO HOIST
AN ADVY. FARTHER W...LACKING SYNOPTIC FORCING...NOTHING MORE THAN
DEVELOPING CHC POPS/SCT -SHSN APPEAR REASONABLE.
850MB TEMPS FALL ANOTHER DEGREE OR TWO THU...BUT EVEN THAT WILL
STILL NOT BE QUITE COLD ENOUGH FOR LES. WITH ANY DEEPER MOISTURE
EXITING AND SINCE THERE WILL PROBABLY BE SOME NEGATIVE IMPACT DUE TO
DAYTIME HEATING WITH HIGHER SUN ANGLE AT THIS TIME OF YEAR...SCT
-SHSN OFF THE LAKE SHOULD WIND DOWN DURING THE DAY.
.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 426 PM EST WED FEB 27 2013
PREFERRED THE 00Z/27 ECMWF AND GLOBAL GEM OVER THE 12Z/27 GFS FOR
THE ENTIRE LONG TERM SINCE THE GFS HAS DISPLAYED POOR RUN TO RUN
CONTINUITY AND LACKS AGREEMENT WITH OTHER MODELS.
KEPT DIMINISHING CHANCES OF LAKE EFFECT SNOW THU NIGHT INTO EARLY
FRI IN AREAS FAVORED BY NE LOW LEVEL WINDS...BUT PUSHED BACK WHEN
POPS GO AWAY ENTIRELY BY AROUND 3 HOURS TO 18Z FRI. AFTER
THAT...VERY DRY LOW LEVELS ASSOCIATED WITH A SFC AND 500MB RIDGE
PUSHING INTO THE CWA. LOW LEVEL FLOW WILL CONTINUE TO BE OUT OF THE
N/NE UNTIL THE SFC RIDGE AXIS COMPLETELY PASSES SUN NIGHT WITH
SLIGHTLY COLDER 850MB TEMPS...SO WILL KEEP INCREASED CLOUD COVER NEAR
LAKE SUPERIOR. MAY SEE A BRIEF RETURN OF NE FLOW LES LATE FRI NIGHT
WITH THE PASSAGE OF A 500MB TROUGH...BUT ANY ACCUMULATIONS WILL BE
MINOR.
THE STORY FOR SUN THROUGH NEXT WED IS THAT A 500MB LOW WILL MOVE
OVER THE CWA THROUGH TUE BEFORE MOVE S ON WED. AT THE SAME
TIME...INCREASINGLY STRONG SFC RIDGING WILL MOVE INTO THE CWA...SO
PRECIP WILL BE AT A MINIMUM. PRECIP...IF ANY...WILL BE MINOR SO
SLIGHT CHANCE POPS AT BEST SEEM APPROPRIATE.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1238 PM EST WED FEB 27 2013
GUSTY N/NE WINDS WILL BE THE RULE AT KIWD/KCMX/KSAW THRU THIS FCST
PERIOD AS TIGHT PRES GRADIENT REMAINS IN PLACE ACROSS THE UPPER GREAT
LAKES. WIND DIRECTION IS MOST FAVORABLE FOR ENHANCED WINDS AT
KSAW...AND GUSTS THERE SHOULD BE IN THE 20-30KT RANGE THROUGHOUT THE
FCST PERIOD. AT KIWD...UPSLOPE N/NNE WINDS WILL LIKELY KEEP LOW MVFR
CIGS IN PLACE THRU THE FCST PERIOD. AS AIR MASS COOLS SLIGHTLY...
LAKE EFFECT -SHSN MAY GET UNDERWAY TONIGHT...BUT EXPECTATION IS FOR
ANY SHSN TO BE LIGHT AND NOT SIGNIFICANTLY REDUCE VIS. AT KCMX...LOW
CLOUDS HAVE SCATTERED OUT...BUT LOWER CLOUDS TO THE NE OF LAKE
SUPERIOR SHOULD ADVECT SW AND BRING A RETURN TO MVFR CIGS AT KCMX
LATE IN THE AFTN. MAY SEE A FEW FLURRIES LATER TONIGHT AT KCMX. AT
KSAW...IDEAL USPLOPE FLOW AND PERIODS OF -SN SHOULD RESULT IN IFR
CONDITIONS PREVAILING FOR THE NEXT SEVERAL HRS. SOME IMPROVEMENT TO
LOW MVFR SHOULD OCCUR LATE AFTN WITH LOW MVFR CONDITIONS CONTINUING
THRU THU MORNING UNDER UPSLOPE NORTHERLY FLOW.
&&
.MARINE...(FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 426 PM EST WED FEB 27 2013
TIGHT PRES GRADIENT BTWN HIGH PRES TO THE N AND NW AND LOW PRES
TRACKING THRU THE LWR LAKES WILL RESULT IN NORTHEASTERLY WINDS OF
20-30KT ACROSS LAKE SUPERIOR THRU THU. GALE FORCE GUSTS SHOULD BE
FREQUENT ENOUGH TO MAINTAIN GALE WARNING FOR THE E HALF OF LAKE
SUPERIOR. IN ADVANCE OF HIGH PRES RIDGE BUILDING TOWARD THE AREA
FRI...TIGHT PRES GRADIENT WILL REMAIN...RESULTING IN CONTINUED
20-30KT NE WINDS. THE STRONG WINDS/HIGH WAVES AND INFLUX OF COLDER
AIR WILL RESULT IN FREEZING SPRAY DEVELOPING TONIGHT AND CONTINUING
THRU FRI NIGHT. HVY FREEZING SPRAY MAY OCCUR FOR A TIME THU
NIGHT/FRI MORNING. WINDS WILL THEN DIMINISH FROM W TO E FRI NIGHT AS
HIGH PRES RIDGE MOVES CLOSER. ON SAT...WINDS SHOULD BE BLO 20KT
ACROSS THE ENTIRE LAKE. LIGHT WINDS...MOSTLY 10KT OR LESS...ARE
EXPECTED SUN/MON AS SFC HIGH PRES RIDGE WILL EXTEND FROM HUDSON BAY
S ACROSS THE UPPER LAKES.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
GALE WARNING UNTIL 10 AM EST THURSDAY FOR LSZ244-245-248>250-
264>267.
LAKE MICHIGAN...
NONE.
&&
$$
SHORT TERM...ROLFSON
LONG TERM...TITUS
AVIATION...ROLFSON
MARINE...ROLFSON
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
332 AM EST WED FEB 27 2013
.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 428 PM EST TUE FEB 26 2013
WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW PRONOUNCED SPLIT FLOW
CONTINUING ACROSS NAMERICA. IN WHAT HAS BEEN A VERY ACTIVE SRN
STREAM RECENTLY...A WELL-DEFINED MID LEVEL LOW IS MOVING ENE INTO
THE LWR OHIO VALLEY. SRN STREAM RIDGING AHEAD OF FEATURE EXTENDS
FROM JUST OFF THE SE COAST TO SRN NEW ENGLAND AND THEN BACK INTO THE
UPPER LAKES. WITH NRN STREAM WELL N OF HERE...ARCTIC AIR HAS
RETREATED INTO NRN CANADA. CLOSER TO HOME...PESKY STRATOCU HAS
CONTINUED TO PLAGUE UPPER MI TODAY. HOWEVER...ROUGHLY THE W THIRD OF
THE FCST AREA HAS ENJOYED MOSTLY SUNNY SKIES FOR AT LEAST A PORTION
OF THE DAY. THE POCKET OF MOSTLY SUNNY SKIES CURRENTLY OVER THE W IS
SHOWING SIGNS OF EXPANDING EASTWARD AS STRONGER DAYTIME HEATING
UNDER HIGHER LATE FEB SUN ANGLE IS WORKING ON LOWER ALBEDO FORESTED
TERRAIN TO RAISE MIXED LAYER AND THUS MIX OUT THE SHALLOW MOIST
LAYER.
DURING THE SHORT TERM...MAIN FCST ISSUE WILL REVOLVE AROUND
NORTHWARD PROGESS OF A WEAKENING PCPN SHIELD SPREADING N AROUND SRN
STREAM MID LEVEL LOW AS IT TRACKS INTO THE UPPER OHIO VALLEY/LWR
LAKES REGION. EARLY ON...LOW CLOUDS WILL CONTINUE TO PRESENT SOME
ISSUES. CLEARING MAY CONTINUE TO EXPAND E FROM WRN UPPER MI OVER THE
NEXT COUPLE OF HRS...BUT WITH LOSS OF DAYTIME HEATING...STRATOCU
WILL PROBABLY TEND TO SPREAD BACK INTO THE AREAS THAT HAVE
CLEARED...ESPECIALLY IF THE STRATOCU TO THE E AND NE DOES NOT BREAK
UP DURING THE LATE AFTN/EVENING. LATEST VIS SATELLITE IMAGERY DOES
SHOW STRATOCU THINNING OVER ERN LAKE SUPERIOR...SO THERE MAY YET BE
SOME MORE CLEARING DURING THE EVENING. WILL BE A TREND TO MONITOR.
WHILE CLOUDS WILL AGAIN MAKE OR BREAK TEMP FCST...THERE WILL LIKELY
NOT BE AS GREAT OF A TEMP SPREAD TONIGHT AS IN PREVIOUS NIGHTS BTWN
AREAS WITH CLOUDS AND AREAS WITH LESS CLOUD SINCE INCREASING
GRADIENT WINDS WILL LIMIT RADIATIONAL COOLING. TRENDED TEMPS TOWARD
RAW MODEL GUIDANCE WHICH PUTS MIN TEMPS GENERALLY IN THE MID/UPPER
20S.
AS FOR PCPN...THE STRONG ISENTROPIC ASCENT COMPONENT TO PCPN SHIELD
SPREADING N INTO SRN WI/SRN MI ATTM WILL GRADUALLY FADE WITH TIME AS
THE ZONE OF STRONG ASCENT TRANSLATES EASTWARD...RESULTING IN ZONE OF
HEAVIEST PCPN SHIFTING E TOWARD THE LWR LAKES/SRN NEW ENGLAND
TONIGHT/WED MORNING. THUS...A DECAYING SHIELD OF PCPN WILL BE
LIFTING TOWARD UPPER MI TONIGHT/WED MORNING. RECENT MODEL TRENDS
GENERALLY POINT TOWARD A MORE AGGRESSIVE PUSH OF LIGHT SNOW INTO
UPPER MI. GIVEN THE STRONG NORTHWARD PUSH OF PCPN THRU LWR MI ATTM
AND THE LACK OF A LAYER OF VERY DRY AIR AT THE LOWER LEVELS TO THE N
ACROSS UPPER MI...HAVE OPTED TO TREND PCPN CHC SLIGHTLY FARTHER N
THAN PREVIOUS FCST TO ROUGHLY A KERY/KSAW/KIMT LINE AND RAISED POPS
TO HIGH CHC ALONG LAKE MI. WITH 850MB TEMPS NO LWR THAN -8/-9C...
IT`S VERY UNLIKELY THAT ANY LES WILL DEVELOP OFF LAKE SUPERIOR UNDER
STRONG NE CYCLONIC FLOW WED. IF SHIELD OF LIGHT SYNOPTIC SNOW DOES
REACH LAKE SUPERIOR...THEN A LITTLE LAKE COMPONENT WILL BE THERE.
.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 331 AM EST WED FEB 27 2013
THURSDAY THROUGH FRIDAY...VERTICALLY STACKED SURFACE AND UPPER LEVEL
500MB CLOSED LOW LOCATED OVER THE LOWER GREAT LAKES THURSDAY MORNING
WILL SHIFT EASTWARD INTO THE NORTHEASTERN U.S. BY THURSDAY NIGHT. IT
DOES APPEAR AS THOUGH ENOUGH MOISTURE WILL REMAIN IN PLACE DURING
THIS TIME PERIOD TO KEEP LAKE EFFECT SNOW SHOWERS OVER AREAS FAVORED
BY A NORTH-NORTHEAST WIND. H850 TEMPERATURES ARE EXPECTED TO COOL TO
AROUND -10 TO -12C WHICH WOULD BE SUPPORTIVE OF LAKE EFFECT SNOW
SHOWERS AS LAKE TEMPERATURES ARE AVERAGING BETWEEN 1 AND 2C. AS
MENTIONED BY THE PREVIOUS SHIFT INVERSION HEIGHTS LOOK TO REMAIN
AROUND 3-4KFT...THIS COUPLED WITH A FAIRLY SHALLOW CLOUD LAYER WOULD
HELP TO LIMIT SNOW ACCUMULATION AS LITTLE IF ANY MOISTURE/LIFT IS
COLLOCATED WITH THE DGZ. LATE THURSDAY NIGHT SURFACE HIGH PRESSURE
WILL BUILD FROM JAMES BAY INTO THE UPPER GREAT LAKES. AT THE SAME
TIME A 500MB RIDGE WILL BUILD ACROSS THE AREA AS WELL. THE
COMBINATION OF WARMING ALOFT ALONG WITH DRY AIR FROM CANADA WRAPPING
IN FROM THE NORTH WILL HELP DIMINISH THE SNOW SHOWERS THROUGH THE
EARLY MORNING HOURS FRIDAY. THE REMAINDER OF FRIDAY LOOKS TO BE
DRY AT THIS POINT.
FRIDAY NIGHT THROUGH SUNDAY NIGHT...THE SURFACE RIDGE AND DRY AIR
ARE PROGGED TO REMAIN IN PLACE OVER MUCH OF THE UPPER GREAT LAKES
REGION THROUGH THIS TIME PERIOD HELPING TO LIMIT PRECIPITATION
CHANCES. THE LACK OF MOISTURE WILL ALSO HELP TO KEEP SKIES PARTLY
CLOUDY TO MOSTLY CLEAR THROUGH THIS TIME FRAME AS WELL. TEMPERATURES
ARE EXPECTED TO BE NEAR TO SLIGHTLY BELOW NORMAL THROUGH THIS TIME
PERIOD AS H850 TEMPS ARE EXPECTED TO BE BETWEEN -12C AND -14C.
MONDAY THROUGH TUESDAY NIGHT...UPPER LEVEL 500MB TROUGH IS EXPECTED
TO REMAIN IN PLACE OVER MUCH OF THE EASTERN SEABOARD THROUGH THIS
TIME PERIOD AS SHOWN BY THE 00Z GFS/EC/GEM. MONDAY MORNING A LOW
PRESSURE SYSTEMS IS PROGGED TO DEVELOP OVER THE CENTRAL PLAINS AT
THE SAME TIME THAT AN UPPER LEVEL 500MB TROUGH DIGS INTO THE PLAINS.
MODELS ARE IN GENERAL AGREEMENT THAT THE LOW WILL REMAIN SOUTH OF
THE UPPER PENINSULA AS THE SURFACE HIGH PRESSURE SYSTEM REMAINS IN
PLACE OVER MUCH OF THE UPPER MIDWEST...SHIFTING SLIGHTLY WEST MONDAY
NIGHT INTO TUESDAY MORNING. THE 00Z GFS/EC ALONG WITH THE GFS
ENSEMBLE MEMBERS KEEP THE LOW SOUTH OF THE AREA...WITH THE LOW
PASSING ALONG OR JUST NORTH OF THE AR/MO BORDER. MODELS ALSO
INDICATED COLDER AIR AT H850 SHIFTING INTO THE REGION WITH WINDS OUT
OF THE NORTH. H850 TEMPS ARE PROGGED TO BE BETWEEN -10 AND -13C
WHILE MOISTURE BETWEEN 1000-850MB IS EXPECTED TO INCREASE. THIS
SHOULD ALLOW LAKE EFFECT SNOW SHOWERS TO DEVELOP OVER NORTH WIND
FAVORED SNOW BELTS. DECIDED TO MENTION ONLY SLIGHT CHANCES MONDAY
NIGHT INTO TUESDAY AS THIS IS STILL SEVERAL DAYS OUT.
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1201 AM EST WED FEB 27 2013
MOIST NE FLOW SHOULD GENERALLY MAINTAIN MVFR CLOUDS THROUGH PD AT
ALL TAF SITES. DOWNSLOPING FLOW AT KCMX COULD PERHAPS LEAD TO BRIEF
BREAKS IN CLOUDS THERE...BUT OTHERWISE INCREASINGLY MOIST NE FLOW
SHOULD ENSURE LOW CLOUDS THROUGH FCST PD. KSAW COULD SEE SOME
AFTERNOON FLURRIES FROM DEEPER MOISTURE WRAPPING BACK INTO AREA FROM
SYSTEM LIFTING THROUGH LOWER LAKES. TIGHTENING PRES GRAD WILL ALLOW
NE WINDS TO GUST NEAR 25 KTS BY LATE WED MORNING/EARLY
AFTERNOON...ESPECIALLY AT KSAW
&&
.MARINE...(FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 428 PM EST TUE FEB 26 2013
TIGHTENING PRES GRADIENT BTWN HIGH PRES TO THE N AND NW AND LOW PRES
TRACKING THRU THE LWR OHIO VALLEY TO LWR LAKES WILL RESULT IN
NORTHEASTERLY WINDS ACROSS LAKE SUPERIOR INCREASING TO 20-30KT
TONIGHT THRU WED. MIGHT SEE A FEW GALE FORCE GUSTS WED AFTN OVER THE
E HALF. EVEN THOUGH THE LOW CONTINUES TO MOVE E THU...THE HIGH
BUILDING TOWARD THE AREA FROM N WILL MAINTAIN A TIGHT PRES
GRADIENT...RESULTING IN CONTINUED 20-30KT WINDS WITH SOME GALE FORCE
GUSTS POSSIBLE OVER THE E HALF THRU THU MORNING. WINDS WILL THEN
VERY SLOWLY DIMINISH FROM W TO E FRI/SAT AS THE HIGH PRES MOVES
CLOSER...BUT IT WILL PROBABLY BE SAT BEFORE WINDS DROP BLO 20KT
ACROSS THE ENTIRE LAKE. THE PERIOD OF STRONG WINDS WED NIGHT THRU
FRI WILL ALSO BRING THE POTENTIAL FOR FREEZING SPRAY. LIGHT WINDS
UNDER 10KT ARE EXPECTED SUN AS SFC HIGH PRES RIDGE WILL EXTEND FROM
HUDSON BAY S ACROSS LAKE SUPERIOR.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
GALE WARNING FROM 7 PM THIS EVENING TO 10 AM EST THURSDAY FOR
LSZ244-245-248>250-264>267.
LAKE MICHIGAN...
NONE.
&&
$$
SHORT TERM...ROLFSON
LONG TERM...KEC
AVIATION...VOSS
MARINE...ROLFSON
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
1202 AM EST WED FEB 27 2013
.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 428 PM EST TUE FEB 26 2013
WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW PRONOUNCED SPLIT FLOW
CONTINUING ACROSS NAMERICA. IN WHAT HAS BEEN A VERY ACTIVE SRN
STREAM RECENTLY...A WELL-DEFINED MID LEVEL LOW IS MOVING ENE INTO
THE LWR OHIO VALLEY. SRN STREAM RIDGING AHEAD OF FEATURE EXTENDS
FROM JUST OFF THE SE COAST TO SRN NEW ENGLAND AND THEN BACK INTO THE
UPPER LAKES. WITH NRN STREAM WELL N OF HERE...ARCTIC AIR HAS
RETREATED INTO NRN CANADA. CLOSER TO HOME...PESKY STRATOCU HAS
CONTINUED TO PLAGUE UPPER MI TODAY. HOWEVER...ROUGHLY THE W THIRD OF
THE FCST AREA HAS ENJOYED MOSTLY SUNNY SKIES FOR AT LEAST A PORTION
OF THE DAY. THE POCKET OF MOSTLY SUNNY SKIES CURRENTLY OVER THE W IS
SHOWING SIGNS OF EXPANDING EASTWARD AS STRONGER DAYTIME HEATING
UNDER HIGHER LATE FEB SUN ANGLE IS WORKING ON LOWER ALBEDO FORESTED
TERRAIN TO RAISE MIXED LAYER AND THUS MIX OUT THE SHALLOW MOIST
LAYER.
DURING THE SHORT TERM...MAIN FCST ISSUE WILL REVOLVE AROUND
NORTHWARD PROGESS OF A WEAKENING PCPN SHIELD SPREADING N AROUND SRN
STREAM MID LEVEL LOW AS IT TRACKS INTO THE UPPER OHIO VALLEY/LWR
LAKES REGION. EARLY ON...LOW CLOUDS WILL CONTINUE TO PRESENT SOME
ISSUES. CLEARING MAY CONTINUE TO EXPAND E FROM WRN UPPER MI OVER THE
NEXT COUPLE OF HRS...BUT WITH LOSS OF DAYTIME HEATING...STRATOCU
WILL PROBABLY TEND TO SPREAD BACK INTO THE AREAS THAT HAVE
CLEARED...ESPECIALLY IF THE STRATOCU TO THE E AND NE DOES NOT BREAK
UP DURING THE LATE AFTN/EVENING. LATEST VIS SATELLITE IMAGERY DOES
SHOW STRATOCU THINNING OVER ERN LAKE SUPERIOR...SO THERE MAY YET BE
SOME MORE CLEARING DURING THE EVENING. WILL BE A TREND TO MONITOR.
WHILE CLOUDS WILL AGAIN MAKE OR BREAK TEMP FCST...THERE WILL LIKELY
NOT BE AS GREAT OF A TEMP SPREAD TONIGHT AS IN PREVIOUS NIGHTS BTWN
AREAS WITH CLOUDS AND AREAS WITH LESS CLOUD SINCE INCREASING
GRADIENT WINDS WILL LIMIT RADIATIONAL COOLING. TRENDED TEMPS TOWARD
RAW MODEL GUIDANCE WHICH PUTS MIN TEMPS GENERALLY IN THE MID/UPPER
20S.
AS FOR PCPN...THE STRONG ISENTROPIC ASCENT COMPONENT TO PCPN SHIELD
SPREADING N INTO SRN WI/SRN MI ATTM WILL GRADUALLY FADE WITH TIME AS
THE ZONE OF STRONG ASCENT TRANSLATES EASTWARD...RESULTING IN ZONE OF
HEAVIEST PCPN SHIFTING E TOWARD THE LWR LAKES/SRN NEW ENGLAND
TONIGHT/WED MORNING. THUS...A DECAYING SHIELD OF PCPN WILL BE
LIFTING TOWARD UPPER MI TONIGHT/WED MORNING. RECENT MODEL TRENDS
GENERALLY POINT TOWARD A MORE AGGRESSIVE PUSH OF LIGHT SNOW INTO
UPPER MI. GIVEN THE STRONG NORTHWARD PUSH OF PCPN THRU LWR MI ATTM
AND THE LACK OF A LAYER OF VERY DRY AIR AT THE LOWER LEVELS TO THE N
ACROSS UPPER MI...HAVE OPTED TO TREND PCPN CHC SLIGHTLY FARTHER N
THAN PREVIOUS FCST TO ROUGHLY A KERY/KSAW/KIMT LINE AND RAISED POPS
TO HIGH CHC ALONG LAKE MI. WITH 850MB TEMPS NO LWR THAN -8/-9C...
IT`S VERY UNLIKELY THAT ANY LES WILL DEVELOP OFF LAKE SUPERIOR UNDER
STRONG NE CYCLONIC FLOW WED. IF SHIELD OF LIGHT SYNOPTIC SNOW DOES
REACH LAKE SUPERIOR...THEN A LITTLE LAKE COMPONENT WILL BE THERE.
.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 428 PM EST TUE FEB 26 2013
LITTLE CHANGES TO THE LONG TERM FROM 24 HOURS AGO...WITH THE
MAIN ITEM OF DIFFERENCE A SLIGHT WOBBLE TO THE NORTHWEST WITH THE
SYSTEM CURRENTLY MOVING THROUGH THE MID MISSISSIPPI VALLEY THAT
WILL MOVE THROUGH THE LOWER GREAT LAKES. THIS SLIGHT
ADJUSTMENT...PUSHES THE PRECIPITATION A TOUCH FARTHER INLAND FROM
LAKE MICHIGAN. BUT AS THE LONG TERM PERIOD BEGINS...THE LOW WILL
START IT/S EASTWARD SHIFT TOWARDS NEW YORK AND DIMINISH THE SNOW
ALONG THE LAKE MICHIGAN SHORELINE.
ATTENTION THEN TURNS TO THE AMOUNT OF MOISTURE AND COLD AIR IN THE
LOWER LEVELS TO SUPPORT LAKE ENHANCED AND UPSLOPE SNOW SHOWERS.
LATEST TRENDS IN THE MOISTURE AND COLD AIR /850MB TEMPERATURES
FALLING FROM -9C AT WEDNESDAY NIGHT TO -13C BETWEEN 900-850MB BY
THURSDAY AFTERNOON/ LEADS TO GREATER CONFIDENCE IN SCATTERED SNOW
SHOWERS OCCURRING FOR LOCATIONS NEAR LAKE SUPERIOR FROM PICTURED
ROCKS AND WESTWARD. INVERSION HEIGHTS AROUND 3-4KFT SHOULD KEEP THE
INTENSITY IN CHECK AND HELPS KEEP LAKE INDUCED CAPES BELOW 200
J/KG. THUS...WILL BUMP POPS UP 5-10 PERCENT INTO HIGHER END CHANCE
CATEGORY. SNOWFALL AMOUNTS SHOULD BE FAIRLY LIGHT...SINCE CLOUD
DEPTH IS FAIRLY LIMITED. WITH THE INITIAL CLOUD LAYER MAINLY BEING
BELOW THE DGZ WEDNESDAY NIGHT...WOULD EXPECT FLAKES TO BE FAIRLY
SMALL. BUT AS THE COLDER AIR ARRIVES...IT DOES ATTEMPT TO PUSH THE
CLOUD LAYER INTO THE DGZ AND HELP SNOW RATIOS. BUT WITH THE LIMITED
CLOUD DEPTH/MOISTURE TO WORK WITH...WOULDN/T EXPECT MUCH MORE THAN
AN INCH OR TWO OF TOTAL ACCUMULATION BY THE TIME IT STARTS WINDING
DOWN ON FRIDAY. THE HIGHEST AMOUNTS WILL BE IN THE FAVORED UPSLOPE
LOCATIONS WITH NORTHEAST WINDS...ESPECIALLY IN/NEAR THE HURON
MOUNTAINS WHICH COULD APPROACH 3 INCHES.
A BUILDING CANADIAN HIGH OVER HUDSON BAY WILL SLIDE A RIDGE SOUTH
INTO THE UPPER GREAT LAKES REGION FRIDAY AND IT WILL REMAIN INTO THE
FIRST PART OF THE NEXT WEEK. THIS WILL WORK TO REDUCE THE INVERSION
HEIGHTS TO 2KFT AND SHOULD BRING AN END TO THE LAKE ENHANCED/EFFECT
BY FRIDAY NIGHT. WILL GO WITH PARTLY CLOUDY SKIES THROUGH THE
WEEKEND...BUT THERE IS SOME CONCERN THAT THERE COULD BE LINGERING
LOW CLOUDS BELOW THE STRENGTHENING INVERSION DURING THAT TIME.
MAIN QUESTION FOR NEXT WEEK WILL BE THE LOCATION OF A SHORTWAVE
CUTTING THROUGH THE UPPER RIDGE OVER THE WESTERN CONUS AND IT/S
INFLUENCE ON THE UPPER TROUGH ON THE EAST COAST. 00Z ECMWF HOLDS
THE TROUGH OVER THE AREA...WHILE THE GFS TRIES TO PUSH THE RIDGE
OVER THE AREA ON MONDAY. THIS HAS THE POTENTIAL FOR WEAKENING THE
SURFACE RIDGE AND PUSHING SOME PRECIPITATION INTO THE AREA ON THE
EAST SIDE OF A LOW MOVING THROUGH CENTRAL PLAINS OR UPPER
MISSISSIPPI VALLEY. WILL RESPECT THE CONSISTENCY SHOWN IN THE ECMWF
OVER THE LAST SEVERAL DAYS AND TRY TO KEEP MUCH OF THE AREA DRY.
HIGH TEMPERATURES ARE STILL LOOKING TO BE BELOW NORMAL THROUGH THE
LONG TERM PERIOD. LOOKING AT THE LONGER RANGE FORECASTS /EVEN THOUGH
SKILL IS FAIRLY LIMITED/...NOT TOO MANY SIGNS OF SPRING FOR THE
FIRST WEEK OR TWO OF MARCH. GFS/ECMWF ENS MEANS ARE SHOWING 850MB
TEMPS BELOW NORMAL THROUGH THE FIRST WEEK AND GFS ENS 500MB MEAN
HEIGHTS ARE SHOWING A TROUGH REMAINING OVER THE EASTERN CONUS
THROUGH THE MIDDLE OF MARCH. AFTER BEING SPOILED BY WARM
MARCH WEATHER IN 2010/2012...ITS LOOKING LIKE MARCH WILL
BE MORE TRADITIONAL TEMPERATURE WISE. UNFORTUNATELY FOR SOME OF THE
LOCATIONS OF CENTRAL UPPER MICHIGAN THAT HAVE SEEN PROLONGED
DRYNESS...THIS PATTERN WON/T BE SUPPORTIVE OF ANY SIGNIFICANT
PRECIPITATION AND MAINLY JUST LIGHT PRECIPITATION FROM CLIPPERS.
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1201 AM EST WED FEB 27 2013
MOIST NE FLOW SHOULD GENERALLY MAINTAIN MVFR CLOUDS THROUGH PD AT
ALL TAF SITES. DOWNSLOPING FLOW AT KCMX COULD PERHAPS LEAD TO BRIEF
BREAKS IN CLOUDS THERE...BUT OTHERWISE INCREASINGLY MOIST NE FLOW
SHOULD ENSURE LOW CLOUDS THROUGH FCST PD. KSAW COULD SEE SOME
AFTERNOON FLURRIES FROM DEEPER MOISTURE WRAPPING BACK INTO AREA FROM
SYSTEM LIFTING THROUGH LOWER LAKES. TIGHTENING PRES GRAD WILL ALLOW
NE WINDS TO GUST NEAR 25 KTS BY LATE WED MORNING/EARLY
AFTERNOON...ESPECIALLY AT KSAW
&&
.MARINE...(FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 428 PM EST TUE FEB 26 2013
TIGHTENING PRES GRADIENT BTWN HIGH PRES TO THE N AND NW AND LOW PRES
TRACKING THRU THE LWR OHIO VALLEY TO LWR LAKES WILL RESULT IN
NORTHEASTERLY WINDS ACROSS LAKE SUPERIOR INCREASING TO 20-30KT
TONIGHT THRU WED. MIGHT SEE A FEW GALE FORCE GUSTS WED AFTN OVER THE
E HALF. EVEN THOUGH THE LOW CONTINUES TO MOVE E THU...THE HIGH
BUILDING TOWARD THE AREA FROM N WILL MAINTAIN A TIGHT PRES
GRADIENT...RESULTING IN CONTINUED 20-30KT WINDS WITH SOME GALE FORCE
GUSTS POSSIBLE OVER THE E HALF THRU THU MORNING. WINDS WILL THEN
VERY SLOWLY DIMINISH FROM W TO E FRI/SAT AS THE HIGH PRES MOVES
CLOSER...BUT IT WILL PROBABLY BE SAT BEFORE WINDS DROP BLO 20KT
ACROSS THE ENTIRE LAKE. THE PERIOD OF STRONG WINDS WED NIGHT THRU
FRI WILL ALSO BRING THE POTENTIAL FOR FREEZING SPRAY. LIGHT WINDS
UNDER 10KT ARE EXPECTED SUN AS SFC HIGH PRES RIDGE WILL EXTEND FROM
HUDSON BAY S ACROSS LAKE SUPERIOR.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&
$$
SHORT TERM...ROLFSON
LONG TERM...SRF
AVIATION...VOSS
MARINE...ROLFSON
AREA FORECAST DISCUSSION
NWS TWIN CITIES/CHANHASSEN MN
249 PM CST WED FEB 27 2013
.DISCUSSION...
STACKED LOW PRESSURE SYSTEM OVER THE EASTERN GREAT LAKES WILL
CONTINUE TO SPONSOR CLOUDS OVER THE LOCAL FORECAST AREA ON ITS
WESTERN PERIPHERY...ALONG WITH WEAK LIFT OVER WEST CENTRAL WI.
HAVE INCLUDED HIGH POPS OVER WEST CENTRAL WI THIS EVENING. HAVE ALSO
INCLUDED A MENTION OF SCATTERED FLURRIES FROM WEST INTO SOUTH
CENTRAL MN WHERE WEAK FRONTOGENESIS IS PROGGED FROM 700-600MB
TONIGHT INTO THURSDAY MORNING.
DESPITE THE EXTENSIVE CLOUD COVER...TEMPS HAVE WARMED INTO THE
UPPER 20S TO UPPER 30S NEARLY CWA-WIDE TODAY. CLOUDS AND WINDS
HOLD TIGHT TONIGHT...SO THINK MOS NUMBERS APPEAR TOO COLD. HAVE
LEANED TOWARD THE BIAS CORRECTED MOS...WHICH YIELDS UPPER TEENS TO
UPPER 20S FOR LOWS TONIGHT.
THURSDAY THROUGH SUNDAY WILL BE RATHER BENIGN LOCALLY...AS THE
AREA REMAINS WEDGED BETWEEN A NORTHEASTERN CONUS TROUGH AND A
BROAD WESTERN RIDGE. NORTHERLY FLOW WILL KEEP TEMPERATURES ON THE
COOL SIDE OF NORMAL THROUGH THE WEEKEND HOWEVER...WITH HIGHS
GENERALLY RUNNING 5 TO 10 DEGREES BELOW CLIMATOLOGY FOR EARLY
MARCH. SINGLE DIGIT LOWS APPEAR LIKELY FOR THE MAJORITY OF THE
FORECAST AREA ON BOTH WEEKEND MORNINGS AS WELL.
THE 12Z SUITE OF MODELS TRENDED TO A SCENARIO MORE FAVORABLE FOR
SNOWFALL IN CENTRAL/SOUTHERN MN...NAMELY THE ECMWF WHICH HAD BEEN
THE MOST OPPOSED PRIOR TO TODAY. IT NOW TRACKS A SURFACE LOW
ACROSS SOUTH DAKOTA AND IOWA...WITH A PROLONGED PERIOD OF
MEASURABLE SNOWFALL FROM WEST INTO SOUTH CENTRAL MN. WHILE MODELS
ARE STILL NOTABLY VARIABLE REGARDING THE TRACK/AMPLITUDE OF THIS
TROUGH...THE RECENT CHANGE OF THE ECMWF HAS INCREASED CONFIDENCE
FOR AT LEAST MEASURABLE SNOW LOCALLY. HAVE THEREFORE INCREASED
POPS TO 50-60 PERCENT FOR WEST/SOUTH CENTRAL MN ON MONDAY AND
MONDAY NIGHT...WITH 20-40S FROM CENTRAL MN INTO WEST CENTRAL WI.
REGARDING TEMPERATURES IN THE EXTENDED...HIGHS SHOULD GENERALLY
RANGE AROUND 5 DEGREES BELOW NORMAL FROM MONDAY THROUGH THE MIDDLE
OF NEXT WEEK...WITH LOWS A FEW DEGREES ON EITHER SIDE OF NORMAL.
&&
.AVIATION.../18Z TAF ISSUANCE/
TERMINALS WILL BE UNDER THE INFLUENCE OF EXPANSIVE VERTICALLY
STACKED AND OCCLUDED LOW NOW NEAR DETROIT THIS ENTIRE TAF PERIOD.
FOR THESE TAFS...FAVORED THE RAP HEAVILY...BLENDED A BIT WITH LAMP
GUIDANCE. THE 925 MB RAP RH HAS BEEN PERFORMING WELL WITH ERODING
OUT WEST END OF MVFR CIGS ACROSS ERN MN. THE RAP HAS BEEN
CONSISTENT WITH PUSHING THESE CIGS EAST THROUGH THE
MORNING...BEFORE QUICKLY BRINGING THIS MOISTURE SOUTHWEST ACROSS
THE REST OF THE MPX CWA THIS AFTERNOON. FOR BRINGING CIGS BACK IN
TO RWF/AXN/STC...BLENDED RAP TIMING IN WITH THE SLOWER LAMP
GUIDANCE...THOUGH DID FAVOR THE RAP. ONCE THESE CLOUDS MOVE
IN...HEIGHTS SHOULD BE FAIRLY CONSISTENT THE REST OF THE TAF
PERIOD...WITH NO SIGNS OF SIGNIFICANT CLEARING WORKING INTO THE
MPX AREA UNTIL CLOSER TO 00Z...OR LATE THU AFTERNOON. BESIDE
CLOUDS...ALSO SEEING A BAND OF MAINLY MVFR SNOW ACROSS CENTRAL WI
SLOWLY WORKING WEST. HRRR REFLECTIVITY FORECAST HAS HAD A GOOD
HANDLE ON THIS SNOW THIS MORNING...SO FOLLOWED IT FOR TIMING SNOW
ACROSS WRN WI. WILL START OFF EAU WITH -SN...WITH THE EXPECTATION
THAT SNOW SHOULD BREAK OUT THERE BY 1830Z. MAINLY MVFR VIS
RESTRICTIONS ARE EXPECTED...THOUGH WITH THE OCCASIONAL IFR VIS
EAST OF EAU...DID KEEP A TEMPO IFR GROUP FOR A BIT THIS AFTERNOON.
THIS SNOW WILL LIKELY GRAZE RNH AND STAY SE OF MSP...THOUGH MAY
IMPACT FIELD SUCH AS K21D AND KSGS. FOR WINDS...NOT EXPECTING MUCH
VARIATION IN DIRECTION THIS PERIOD...WITH JUST AN EVERY SO GRADUAL
BACKING TOWARD THE NNW EXPECTED. WILL CONTINUE WITH GUSTS INTO
THIS EVENING...BUT THINGS LOOKS TO SETTLE DOWN TONIGHT...WITH NO
GUSTS EXPECTED TOMORROW WITH TYPICAL DIURNAL STRENGTHENING.
KMSP...RAP HAS BEEN PRETTY CONSISTENT WITH RETURN TO VFR CIGS
CURRENTLY OBSERVED. CONFIDENCE IS HIGH WE WILL RETURN TO AROUND 2K
FT CIGS..BUT THERE IS LESS CONFIDENCE ON WHEN THEY RETURN...WITH
IT POSSIBLY BEING CLOSER TO 00Z BEFORE GOING BACK TO MVFR. IN
ADDITION...BAND OF SNOW OUT BY EAU WILL MAKE A RUN FOR MSP...AND
BASED ON THE RAP/HRRR...MAY SEE A BRIEF SNOW SHOWER BETWEEN 00Z
AND 03Z...THOUGH CONFIDENCE IN THIS HAPPENING NOT HIGH ENOUGH TO
INCLUDE IN THE TAF ATTM. OTHER CONCERN THIS TAF PERIOD WILL BE
WITH CIG HEIGHTS. KEPT THEM ABOVE 017 FOR NOW...BUT CERTAINLY IS
POSSIBLE THAT CIGS COULD DROP TO AROUND 015 LATE TONIGHT INTO THU
MORNING. ANY IMPROVEMENTS BACK TO VFR NOT EXPECTED UNTIL NEAR THE
END OF OR SHORTLY AFTER THIS TAF PERIOD.
/OUTLOOK FOR KMSP/
FRI...VFR WITH MVFR CIGS POSSIBLE. N WIND 5-10 KTS.
SAT...VFR. N WIND 5 KTS.
SUN...VFR. SE WIND 5 KTS.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
LS/MPG
AREA FORECAST DISCUSSION
NWS TWIN CITIES/CHANHASSEN MN
1150 AM CST WED FEB 27 2013
.UPDATE...
18Z AVIATION DISCUSSION ADDED BELOW.
&&
.PREV DISCUSSION.../ISSUED AT 356 AM CST WED FEB 27 2013/
OVERVIEW...ONLY MINOR ADJUSTMENTS TO POPS/WX/TEMPS WITH THE
MORNING FORECAST PACKAGE. LIGHT SNOW POSSIBLE IN WEST CENTRAL WI
THIS AFTERNOON AND EVENING. VERY LIGHT SNOW OR FLURRIES COULD MAKE
IT INTO FAR EASTERN MN...BUT KEPT THE TWIN CITIES METRO SNOW FREE
AT THIS POINT. WE REMAIN ON THE EASTERN FRINGE OF A CLIPPER SYSTEM
ON MONDAY.
PLENTY OF CLOUD COVER AT MULTIPLE LEVELS ACROSS MN/WI IN RESPONSE
TO LARGE TROUGH STRETCHING FROM THE ROCKIES TO THE EAST COAST.
THE CENTER OF THE LONG SINCE OCCLUDED CYCLONE IS LOCATED ALONG THE
MI/OH BORDER EARLY THIS MORNING...BUT THE WESTWARD EXTENSION OF
THE TROUGH IS STILL SPREADING MODERATE SNOW ACROSS WI AND IA. OUR
WESTERN CWA COULD EVEN GET IN ON SOME LIGHT SNOW LATE THIS MORNING
AND AFTERNOON. 27.00Z NAM IS PROBABLY THE MOST AGGRESSIVE WITH THE
WESTWARD PROPAGATION OF A 700-600 MB FGEN BAND AND OMEGA INTO WEST
CENTRAL WI. ASSORTED SHORT-RANGE MODEL GUIDANCE...SUCH AS THE
HRRR/RAP/HOP-WRF SHOW A BAND OF SYNTHETIC REFLECTIVITY MOVING INTO
WESTERN WI TODAY. AS A RESULT...INCREASED POPS IN A FEW OF OUR WI
COUNTIES...INCLUDING EAU CLAIRE. NOT SUPREMELY CONFIDENT IN
MEASURABLE SNOW...BUT A DUSTING IS PLAUSIBLE AND AS MUCH AS 1/2"
TO 3/4" IS CERTAINLY POSSIBLE. EVEN THE TWIN CITIES METRO COULD
SEE A FEW FLURRIES...ALTHOUGH LEFT THE FORECAST FOR MN MAINLY
WEATHER FREE TODAY AND TONIGHT.
THE SOUTHWARD EXTENT OF THE 0 C 850 MB ISOTHERM IS IMPRESSIVE OVER
THE NEXT SEVERAL DAYS. CURRENTLY...IT STRETCHES FROM ROUGHLY
NORTHERN CALIFORNIA...TO TEXAS...TO NORTHERN SOUTH CAROLINA. BY
THE WEEKEND THE COLD AIR COULD BE AS FAR SOUTH AS SOUTHERN
FLORIDA. WHILE THIS MEANS WELL-BELOW NORMAL TEMPERATURES FOR PARTS
OF THE COUNTRY...IT ACTUALLY REMAINS NEAR NORMAL FOR MN/WI. THERE
WILL HOWEVER BE A SLIGHTLY COOLING TREND LATE THIS WEEK AS
NORTHERLY FLOW KEEPS WEAK COLD AIR ADVECTION GOING FOR THE NEXT
FEW DAYS. THE COLDEST MORNING APPEARS TO BE SATURDAY MORNING WHERE
WE COULD SEE WIDESPREAD SINGLE DIGITS AND LOWER TEENS. IF WE COULD
GUARANTEE NO CLOUD COVER...THEN SOME SITES WOULD CERTAINLY BE
BELOW ZERO GIVEN THE SNOW COVER AND POSITION OF THE SURFACE PRESSURE
RIDGE.
BESIDES THE LIGHT SNOW IN WI TODAY...THE ONLY SIGNIFICANT CHANCE
FOR PRECIP IS WITH A SYSTEM DROPPING SOUTH OUT OF ALBERTA IN THE
MONDAY/TUESDAY TIME FRAME. THE LAST 4-5 RUNS OF THE GFS/ECMWF HAVE
GENERALLY TRENDED WEST WITH THE LOW TRACK...WITH A SLIGHT WOBBLE
HERE AND THERE. WOULD HAVE TO SAY THAT THERE IS DECENT AGREEMENT
BETWEEN THE GEM/GFS/ECMWF/FIM WITH THE SYSTEM EARLY NEXT WEEK. ALL
SOLUTIONS WOULD EITHER FAVOR A MUCH BETTER CHANCE FOR LIGHT SNOW
IN WESTERN MN...OR BEND MOST OF THE PRECIP AROUND THE FORECAST
AREA ALL TOGETHER. VIEWING ALL THE GEFS MEMBERS INDIVIDUALLY...
THERE SEEMS TO ONE TIGHTER CLUSTERING OF LOW TRACKS THAT ARE
SIMILAR TO THE OPERATIONAL 27.00Z GFS. ALTHOUGH...THERE ARE STILL
SEVERAL MEMBERS WITH A MORE EASTERLY SOLUTION...SO THE ENSEMBLE
MEAN IS THEREFORE A BIT FARTHER EAST THAN THE 00Z GFS. RIGHT NOW
THE AXIS OF HEAVIEST QPF FALLS IN THE DAKOTAS AND/OR NORTHERN
NE...WITH 0.30-0.40"...WHICH WOULD BE GOOD ENOUGH FOR A HIGH END
ADVISORY OR A LOW END WARNING. WE`LL HAVE TO WATCH TO SEE IF THERE
IS AN EASTWARD TREND WITH TIME. AT THIS POINT...THERE IS ONLY
ENOUGH CONFIDENCE IN SLIGHT CHANCE/CHANCE POPS.
&&
.AVIATION.../18Z TAF ISSUANCE/
TERMINALS WILL BE UNDER THE INFLUENCE OF EXPANSIVE VERTICALLY
STACKED AND OCCLUDED LOW NOW NEAR DETROIT THIS ENTIRE TAF PERIOD.
FOR THESE TAFS...FAVORED THE RAP HEAVILY...BLENDED A BIT WITH LAMP
GUIDANCE. THE 925 MB RAP RH HAS BEEN PERFORMING WELL WITH ERODING
OUT WEST END OF MVFR CIGS ACROSS ERN MN. THE RAP HAS BEEN
CONSISTENT WITH PUSHING THESE CIGS EAST THROUGH THE
MORNING...BEFORE QUICKLY BRINGING THIS MOISTURE SOUTHWEST ACROSS
THE REST OF THE MPX CWA THIS AFTERNOON. FOR BRINGING CIGS BACK IN
TO RWF/AXN/STC...BLENDED RAP TIMING IN WITH THE SLOWER LAMP
GUIDANCE...THOUGH DID FAVOR THE RAP. ONCE THESE CLOUDS MOVE
IN...HEIGHTS SHOULD BE FAIRLY CONSISTENT THE REST OF THE TAF
PERIOD...WITH NO SIGNS OF SIGNIFICANT CLEARING WORKING INTO THE
MPX AREA UNTIL CLOSER TO 00Z...OR LATE THU AFTERNOON. BESIDE
CLOUDS...ALSO SEEING A BAND OF MAINLY MVFR SNOW ACROSS CENTRAL WI
SLOWLY WORKING WEST. HRRR REFLECTIVITY FORECAST HAS HAD A GOOD
HANDLE ON THIS SNOW THIS MORNING...SO FOLLOWED IT FOR TIMING SNOW
ACROSS WRN WI. WILL START OFF EAU WITH -SN...WITH THE EXPECTATION
THAT SNOW SHOULD BREAK OUT THERE BY 1830Z. MAINLY MVFR VIS
RESTRICTIONS ARE EXPECTED...THOUGH WITH THE OCCASIONAL IFR VIS
EAST OF EAU...DID KEEP A TEMPO IFR GROUP FOR A BIT THIS AFTERNOON.
THIS SNOW WILL LIKELY GRAZE RNH AND STAY SE OF MSP...THOUGH MAY
IMPACT FIELD SUCH AS K21D AND KSGS. FOR WINDS...NOT EXPECTING MUCH
VARIATION IN DIRECTION THIS PERIOD...WITH JUST AN EVERY SO GRADUAL
BACKING TOWARD THE NNW EXPECTED. WILL CONTINUE WITH GUSTS INTO
THIS EVENING...BUT THINGS LOOKS TO SETTLE DOWN TONIGHT...WITH NO
GUSTS EXPECTED TOMORROW WITH TYPICAL DIURNAL STRENGTHENING.
KMSP...RAP HAS BEEN PRETTY CONSISTENT WITH RETURN TO VFR CIGS
CURRENTLY OBSERVED. CONFIDENCE IS HIGH WE WILL RETURN TO AROUND 2K
FT CIGS..BUT THERE IS LESS CONFIDENCE ON WHEN THEY RETURN...WITH
IT POSSIBLY BEING CLOSER TO 00Z BEFORE GOING BACK TO MVFR. IN
ADDITION...BAND OF SNOW OUT BY EAU WILL MAKE A RUN FOR MSP...AND
BASED ON THE RAP/HRRR...MAY SEE A BRIEF SNOW SHOWER BETWEEN 00Z
AND 03Z...THOUGH CONFIDENCE IN THIS HAPPENING NOT HIGH ENOUGH TO
INCLUDE IN THE TAF ATTM. OTHER CONCERN THIS TAF PERIOD WILL BE
WITH CIG HEIGHTS. KEPT THEM ABOVE 017 FOR NOW...BUT CERTAINLY IS
POSSIBLE THAT CIGS COULD DROP TO AROUND 015 LATE TONIGHT INTO THU
MORNING. ANY IMPROVEMENTS BACK TO VFR NOT EXPECTED UNTIL NEAR THE
END OF OR SHORTLY AFTER THIS TAF PERIOD.
/OUTLOOK FOR KMSP/
FRI...VFR WITH MVFR CIGS POSSIBLE. N WIND 5-10 KTS.
SAT...VFR. N WIND 5 KTS.
SUN...VFR. SE WIND 5 KTS.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
CLF/MPG
AREA FORECAST DISCUSSION
NWS TWIN CITIES/CHANHASSEN MN
1144 PM CST TUE FEB 26 2013
.AVIATION... /06Z TAF ISSUANCE/
LIFR OR LOWER CONDITIONS SHOULD REMAIN JUST WEST OF KAXN AND KRWF
OVERNIGHT AS DRIER AIR LOW LEVEL AIR CONTINUES TO STREAM IN FROM
THE NORTHEAST. VISIBILITIES BETWEEN 2 AND 4SM IN BR WILL BE
COMMON. MVFR CEILINGS (BKN-OVC020-025) HAVE SPREAD ACROSS KEAU
FROM THE EAST AND WILL SOON REACH KRNH AND KMSP BY 09Z. SHORT TERM
GUIDANCE SUGGESTS THAT THIS WILL LAST THROUGH THE DAY AND THE
UPCOMING NIGHT WITH A SMALL CHANCE FOR VFR LATE WEDNESDAY
AFTERNOON AND EARLY EVENING. HOWEVER...CONFIDENCE IS NOT HIGH
ENOUGH TO STRAY FROM MVFR ATTM. THERE WILL ALSO BE SOME LIGHT SNOW
AT KEAU WEDNESDAY MORNING AND EARLY AFTERNOON. THE BEST PERIOD FOR
SMALL ACCUMULATIONS LOOKS TO BE BETWEEN 14Z AND 20Z. SOME SNOW
SHOWERS COULD REACH KRNH. ALL SITES EXPECTED TO BE AOB 030
WEDNESDAY NIGHT WITH KAXN AOB 010. NORTHERLY WINDS OVERNIGHT NEAR
10 KNOTS INCREASING TO 12-15 KNOTS WITH GUSTS TO 22-25 KNOTS ON
WEDNESDAY.
KMSP...MVFR CEILINGS CURRENTLY ABOUT 50 MILES EAST OF THE
AIRFIELD. ITS DIFFICULT TO CALCULATE THEIR WESTWARD SPEED DUE TO
THE EXTENSIVE HIGH LEVEL OVERCAST ACROSS THE REGION. A ROUGH
ESTIMATE IS 25 KTS WHICH WOULD BRING THE CEILINGS IN BEFORE 07Z.
CHANCES ARE PRETTY HIGH THAT THE MVFR CEILINGS WILL CONTINUE
THROUGH THE TAF PERIOD ALTHOUGH THERE IS A SMALL CHANCE FOR
IMPROVEMENT WEDNESDAY AFTERNOON/EVENING AS THE LOW LEVEL NE FLOW
OFF OF LAKE SUPERIOR ENDS AND BECOMES MORE NORTHERLY. CHANCES THEN
INCREASE AGAIN FOR MVFR CEILINGS OVERNIGHT AND THURSDAY MORNING AS
A TROUGH OF LOW PRESSURE DROPS SOUTH ACROSS THE REGION.
/OUTLOOK FOR KMSP/
THU...MVFR CIGS. N WIND 10 KTS.
FRI...VFR WITH MVFR CIGS POSSIBLE. N WIND 5-10 KTS.
SAT...VFR. N WIND 5 KTS.
&&
.DISCUSSION... /ISSUED AT 233 PM CST TUE FEB 26 2013/
INITIAL CONCERN IS CLOUD COVER OVERNIGHT. DRIER WEDGE IN LOWER
LEVEL CIRCULATING AROUND STORM TO THE SOUTH WAS STRONG ENOUGH THIS
AFTERNOON TO ERODE CLOUDS SOME. ANOTHER SURGE OF MOISTURE APPEARS
TO BE WORKING ACROSS THE UP AND NORTHEAST WI AND IS NOW MOVING
ACROSS WEST CENTRAL WI. LATEST RAP HAS THIS WORKING SOUTHWEST LATE
AFTERNOON INTO THE EVENING...AFFECTING MAINLY SOUTH CENTRAL MN.
STRATUS AND FOG IS NOW ERODING FROM THE NORTH AS WELL...IN DRIER
AIR FLOW OVER NORTHEAST MN. DIFFICULT TO DISCERN HOW FAR SOUTH AND
WEST THIS WILL GO. MODELS TREND MUCH DRIER IN THE 925-850MB LAYER
OVER THE WESTERN AREAS. STILL BELIEVE SIGNIFICANT AMOUNT OF
MID/HIGH CLOUDS WILL CONTINUE TO STREAM NORTH AND WEST OVER NIGHT
AND SHOULD MAINTAIN AT LEAST A MOSTLY CLOUDY SKY OVER MOST OF THE
AREA. FOG SHOULD BE LIMITED TO THE FAR WEST INTO THE EVENING...AND
SHOULDNT BECOME DENSE OR AS WIDESPREAD WITH THE GRADIENT
INCREASING AS WELL AS THE SURFACE WINDS OVERNIGHT.
CONCERN NUMBER TWO REMAINS HOW FAR NORTHWEST SNOW WILL DEVELOP
MAINLY DURING THE DAY WEDNESDAY. MODELS FAIRLY CONSISTENT ON
DRAGGING SNOW INTO FAR SOUTHEAST CWA...WITH THE NAM REMAINING THE
DRIEST. THE GFS IS FARTHER WEST INTO OUR CWA...WITH THE 12Z GEM
AND ECMWF CONFINING POSSIBILITY TO THE FAR SOUTHEAST CORNER OF THE
AREA. IT ALL HINGES ON HOW THE SECONDARY UPPER TROUGH MOVES ACROSS
KANSAS AND MERGES WITH THE UPPER LOW MOVING OVER THE OHIO RIVER
RIVER VALLEY. WILL CONTINUE THE TREND OF LOW END CHANCE POPS OVER
THAT REGION THROUGH WEDNESDAY.
SHOULD SEE SOME CLEARING INTO WEDNESDAY NIGHT FOLLOWING THE STORM
SYSTEM TO THE SOUTHEAST...BUT MODELS TREND ANOTHER SHORT WAVE
DROPPING SOUTHEAST OVER THE DAKOTAS AND MINNESOTA...THURSDAY INTO
FRIDAY. THIS SHOULD YIELD AT LEAST MORE CLOUDS AND THE THREAT OF
SOME FLURRIES...MAINLY OVER THE WESTERN AREAS. THE 12Z ECMWF IS
NOT AS AMPLIFIED WITH THIS FEATURE AND IS A BIT DRIER...SO WILL
LEAVE FLURRY MENTION OUT FOR NOW.
HIGH TEMPERATURES FORECAST SLIGHTLY BELOW NORMAL INTO THE
WEEKEND. NEXT STRONG TROUGH MOVES ASHORE ON THE WEST COAST OVER
THE WEEKEND. LONGER TERM MODELS BRINGING THIS NEXT WAVE/TROUGH
INTO THE AREA MAINLY SUNDAY NIGHT INTO TUESDAY. HAVE INCLUDED
SMALL CHANCE POPS FOR THIS FEATURE AS IT MOVES THROUGH THE AREA
FOR NOW. COULD BE WARM ENOUGH FOR A POSSIBLY MIX AS THE SYSTEM
WORKS INTO THE AREA...AT LEAST INITIALLY.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
RAH/DWE
AREA FORECAST DISCUSSION
NWS BILLINGS MT
837 PM MST THU FEB 28 2013
.SHORT TERM...VALID FOR FRI AND SAT...
UNSTABLE NORTHWEST FLOW WILL PERSIST OVER SOUTHEAST MONTANA
TONIGHT. WEAK SHORT WAVE PUSHING THROUGH THIS AREA WILL BRING
ISOLATED SNOW SHOWER FROM SOUTH OF A LINE FROM LAME DEER EAST TO
EKALAKA. HRRR INDICATING LIGHT PRECIPITATION SHOULD CONTINUE THEIR
THROUGH THE NIGHT. TIS LOOKS ON TRACK AS BOWMAN RADAR WAS ALSO
INDICATING WEAK ECHOE RETURNS OVER THE SOUTHEAST. DID ADJUST WINDS
DOWN IN LIVINGSTON TO BIG TIMBER AND NEAR NYE FOR THIS EVENING AS
PRESSURE GRADIENTS HAVE WEAKEN THE PAST COUPLE OF HOURS. EXPECT
GRADIENT TO INCREASE AFTER MIDNIGHT AS A LEE SIDE TROUGH DEEPENS.
SURFACE HIGH PRESSURE ALSO SETTING UP OVER YELLOWSTONE PARK WHICH
WILL HELP TO SET UP A STRONG PRESSURE GRADIENT ALONG WITH COLD AIR
DRAINAGE. WILL GO AHEAD AND KEEP CURRENT WIND ADVISORY IN PLACE.
WINDS WILL BE INCREASING AFTER MIDNIGHT AND ARE STILL EXPECTED TO
REACH LOW END ADVISORY CRITERIA. REMAINDER OF THE FORECAST ON
TRACK AND NO OTHER CHANGES MADE. RICHMOND
.LONG TERM...VALID FOR SUN...MON...TUE...WED...THU...
THE EXTENDED PERIOD CONTINUES TO BE THE TALE OF TWO WEATHER
SYSTEMS...WITH A SYSTEM IN TO START THE PERIOD ON SUNDAY...AND
ANOTHER TO END THE PERIOD FOR WEDNESDAY NIGHT AND THURSDAY. THE
MODELS SEEM TO BE IN PRETTY GOOD AGREEMENT AS TO THE OVERALL
PATTERN...HOWEVER RUN TO RUN CONSISTENCY HAS NOT AS GOOD WITH
REGARD TO THE FINER DETAILS. A FEW CHANGES WERE MADE THROUGHOUT
THE PERIOD...PRIMARILY WITH REGARD TO THE TIMING OF THE FIRST
SYSTEM.
THE PACIFIC LOW PREVIOUSLY PROGGED INTO THE REGION LATE SUNDAY AND
INTO MONDAY...APPEARS TO BE 12HRS OR SO EARLIER. ADDITIONALLY...THE
SYSTEM NOW APPEARS TO HAVE A BIT MORE SOUTHERLY TRACK...ALLOWING
FOR MORE UPSLOPE FLOW POTENTIAL INTO THE WEST...AS WELL AS SOME
GREATER IMPACTS FROM COLD AIR MIXING WITH THE SUBTROPICAL MOISTURE
TAP. DIFFERENT TIMING NECESSITATED CHANGES TO POPS AND TEMPS FOR
THIS SYSTEM. THEREFORE...EXPANDED EASTWARD AND RAISED POPS
SLIGHTLY FOR SUNDAY THROUGH SUNDAY NIGHT. MAINTAINS HIGHER POPS
THROUGH MONDAY...AS STILL APPEARS THAT TROWEL SHOULD SET UP FOR
GOOD WRAP AROUND POTENTIAL INTO THE EAST. ALSO LOWERED TEMPS FOR
SUNDAY ACROSS THE REGION...BUT ESPECIALLY WEST...AS THIS SYSTEM
SHOULD BRING MUCH COLDER AIR INTO THE REGION AS WELL AS RESTRICT
DIRECT SOLAR HEATING. KEPT EAST A BIT WARMER...ALLOWING FOR SOME
DIURNAL HEATING AT LEAST TO START THE DAY SUNDAY. HIGHS SUNDAY
WILL LIKELY OCCUR EARLY IN THE DAY.
UPPER LEVEL HIGH BUILD INTO THE REGION BEGIN THIS SYSTEM...AND IS
AMPLIFIED BY THE NEXT PACIFIC LOW...BRINGING A WARM UP AND DRY
CONDITIONS TO THE REGION THROUGH WEDNESDAY. THE NEXT PACIFIC
SYSTEM WILL BEGIN PUSH INTO THE HIGH TERRAIN BY WEDNESDAY
NIGHT...AND CONTINUES ACROSS THE REGION THROUGH THURSDAY. THERE
IS STILL SOME UNCERTAINTY WITH THIS SYSTEM...BUT CURRENTLY LOOKS
TO BIT FURTHER SOUTH THAN THE WEEKEND SYSTEM...AND IT SHOULD BRING
ANOTHER SHOT AT WIDESPREAD PRECIP TO THE REGION. DID BUMP POPS UP
SLIGHTLY...BUT NEAR CLIMO. THIS SYSTEM DOES LOOK A BIT COOLER AT
THIS TIME...SO EXPECT TEMPS TO TURN COOLER WEDNESDAY NIGHT OR
THURSDAY. AAG
&&
.AVIATION...
GUSTY SW WINDS WILL CONTINUE TO INCREASE AT KLVM AND BIG TIMBER
TONIGHT...WITH GUSTS AROUND 50 KNOTS LATE TONIGHT. ISOLATED TO
SCATTERED SNOW SHOWERS ARE POSSIBLE OVERNIGHT IN THE
MOUNTAINS...LEADING TO SOME MOUNTAIN OBSCURATIONS...BUT VFR
CONDITIONS ARE EXPECTED TO PREVAIL ELSEWHERE. STC
&&
.PRELIMINARY POINT TEMP/POPS...
FRI SAT SUN MON TUE WED THU
-----------------------------------------------------------
BIL 029/057 037/060 037/049 029/039 022/047 029/048 025/042
10/N 00/N 03/W 53/J 10/B 00/B 33/W
LVM 035/051 033/053 034/045 029/036 020/047 029/046 026/042
21/N 00/N 15/W 43/J 11/B 12/W 43/W
HDN 024/053 034/060 032/051 027/038 018/047 025/049 020/043
10/E 00/B 03/W 65/J 10/B 00/B 23/W
MLS 028/058 036/060 036/054 031/037 020/046 026/047 026/040
11/E 00/B 04/W 76/J 21/B 00/B 23/W
4BQ 025/050 035/055 035/051 031/037 018/043 025/048 022/041
21/B 00/B 02/W 76/J 21/B 00/U 22/W
BHK 024/048 032/055 034/053 030/032 016/038 022/043 026/038
11/B 00/B 03/W 76/J 31/B 00/U 22/W
SHR 018/043 031/052 029/046 026/034 015/042 023/048 019/041
11/B 10/U 02/W 65/J 11/B 00/B 23/J
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...WIND ADVISORY IN EFFECT UNTIL 6 PM MST FRIDAY FOR ZONES
41-65-66.
WY...NONE.
&&
$$
WEATHER.GOV/BILLINGS
AREA FORECAST DISCUSSION
NWS BILLINGS MT
324 AM MST WED FEB 27 2013
.SHORT TERM...VALID FOR TDY AND THU...
A COUPLE OF DYNAMICALLY-WEAK AND MOISTURE-STARVED WAVES ARE HEADED
OUR WAY THE NEXT TWO DAYS...BUT IMPACTS WITH THEM APPEAR MINIMAL.
TODAY...STRATUS BUILT SOUTHEAST INTO MILES CITY AND BAKER BEHIND A
WEAK COLD FRONT OVERNIGHT...SO A PRIMARY FORECAST CONSIDERATION IS
WHEN IT WILL BREAK UP. RAP-BASED SOLUTIONS HOLD THE STRATUS ACROSS
MUCH OF SOUTHEASTERN MT THROUGH THE DAY...WHICH KEEPS HIGHS IN THE
LOWER 30S F EVEN FOR MILES CITY IN THOSE MODEL SIMULATIONS. HAVING
SAID THAT...THE PLANETARY BOUNDARY LAYER PARAMETERIZATION THAT THE
RAP USES IS KNOWN TO BE TOO SLOW IN ERODING STRATUS...SO THAT IDEA
IS PROBABLY THE WORST-CASE SCENARIO. RECENT HRRR RUNS SEEM TO HAVE
A BETTER HANDLE ON THE STRATUS...TAKING IT OUT OF MILES CITY PRIOR
TO 18 UTC...AND LINGERING IT INTO THE AFTERNOON ONLY AROUND BAKER.
WE THUS REDUCED HIGHS INTO THE MID 30S F AT BAKER...BUT DECIDED TO
LEAVE THEM ALONE OVER THE REST OF SOUTHEASTERN MT. HIGHS OVER MOST
OF THE AREA ARE IN LINE WITH THE 00 UTC BIAS-CORRECTED MULTI-MODEL
CONSENSUS...WHICH SUPPORTS READINGS OF 40 TO 45 F AGAIN TODAY WITH
BARE GROUND HELPING OUT WARMING DESPITE MODEST MIXING.
TONIGHT...A WEAK 500-HPA SHORT WAVE TROUGH WILL CROSS THE AREA. WE
LEFT LOW-END POPS IN PLAY FOR CONTINUITY/S SAKE AND OUT OF RESPECT
TO THE 00 UTC GFS...WHICH DOES SIMULATE SOME SHOWERS. THE GFS IDEA
IS ADMITTEDLY A BIT OF AN OUTLIER THOUGH. OTHERWISE...WINDS SHOULD
INCREASE AT BOTH LIVINGSTON AND BIG TIMBER AS THE SURFACE GRADIENT
TIGHTENS WITH THE PASSAGE OF THE SHORT WAVE. IF THE GFS DOES PROVE
CORRECT...WE MAY ACTUALLY NEED TO FURTHER INCREASE WIND SPEEDS FOR
BIG TIMBER. FORECAST LOWS TONIGHT ARE BASED ALMOST ENTIRELY ON THE
00 UTC BIAS-CORRECTED GFS GRIDDED MOS OUTPUT...WHICH HAS PERFORMED
MUCH BETTER THAN MOST COLD-BIASED LOW TEMPERATURE GUIDANCE LATELY.
THU...WEAK COLD AIR ADVECTION ALOFT WILL YIELD MIXING UP TO AROUND
750 HPA IN MOST AREAS...WHICH WILL COMBINE WITH DOWNSLOPE WINDS IN
THE BOUNDARY LAYER TO PROMOTE ANOTHER SEASONABLY MILD DAY. THE GFS
AND WRF-BASED SOLUTIONS LIKE THE NAM AND SREF ARE AT ODDS WITH THE
NEXT WEAK 500-HPA SHORT WAVE...WITH THE LATTER MODELS SUPPORTING A
LOW-END SHOWER CHANCE AGAIN...ESPECIALLY BY THU EVENING. GIVEN THE
MODEL SPREAD...WE CHOSE TO LEAVE OUR MAINLY DRY FORECAST ALONE FOR
NOW. THAT ALSO SERVES TO LIMIT THE NUMBER OF PERIODS CONTAINING 20
OR 30 PERCENT POPS IN WHAT IS GENERALLY A BENIGN PATTERN. SCHULTZ
.LONG TERM...VALID FOR FRI...SAT...SUN...MON...TUE...
MODELS HAVING TROUBLE RESOLVING SMALLER FEATURES THROUGH THE
EXTENDED SO HAVE KEPT A BROADBRUSH APPROACH GOING WITH THIS
PACKAGE. MODELS ARE IN AGREEMENT WITH STRONG UPPER RIDGE
DEVELOPING FOR LATE THURSDAY INTO SUNDAY. DEEP TROF IN THE EASTERN
U.S. WILL BLOCK FLOW ACROSS THE REGION...ESPECIALLY THE NORTHERN
JET STREAM...RESULTING IN RIDGE DEVELOPMENT OVER THE AREA LATE
WEEK INTO THE WEEKEND. 850 TEMPERATURES PUSH DOUBLE DIGITS BY
FRIDAY INTO SATURDAY FOR HIGHS IN THE 50S TO LOWER 60S. THERE IS A
GOOD MOISTURE STREAM OVER RIDING THE RIDGE SO EXPECT A GOOD DEAL
OF MID AND HIGH CLOUD COVER AND A FEW SNOW SHOWERS FOR MOUNTAIN
AREAS. MODEL SPECTRUM DOES SHOW A VERY LARGE SPREAD FOR
TEMPERATURES FRIDAY INTO SATURDAY DUE TO A FEW MODEL SOLUTIONS
HOLDING ONTO COLDER SOLUTION FROM THE PAST FEW DAYS. LATEST RUNS
SEEM SOLIDLY IN THE WARM SIDE OF GUIDANCE AND RECENT MODEL
SOLUTIONS HAVE TRENDED TOO COLD BY 5 TO 10 DEGREES THUS PUSHED CURRENT
FORECAST TOWARD THE HIGH END OF GUIDANCE.
SUNDAY INTO WEDNESDAY LOOKS UNSETTLED AS SEVERAL PACIFIC SYSTEMS
TRY TO BUILD INTO THE AREA. BLOCKING BY DEEP TROF OVER THE EASTERN
U.S. WILL CONTINUE TO PRESENT A PROBLEM FOR EASTERLY MOVEMENT AND
HAVE SEEN MODELS JUMP AROUND FROM SOLUTIONS THAT SIT THESE PACIFIC
DISTURBANCES OVER THE AREA FOR A DAY OR TWO TO OTHER SOLUTIONS
THAT MOVE SYSTEMS IN FROM THE WEST THEN DEFLECT THEM SOUTHWARD
INTO WYOMING AND COLORADO. MODELS BRING THE FIRST OF THE SYSTEMS
INTO THE AREA SUNDAY AFTERNOON...BUT THIS MAY BE A BIT FAST GIVEN
UPSTREAM BLOCK. KEPT TEMPERATURES ON THE WARM END SUNDAY BUT DID
ADD MENTION OF CHANCE POPS TO WESTERN HALF OF FORECAST AREA.
MONDAY INTO WEDNESDAY LOOK UNSETTLED WITH BROADBRUSH 30 AND 40
POPS FOR LOWER ELEVATIONS AND LIKELY POPS FOR THE MOUNTAINS ON
MONDAY...AND CLIMO TYPE POPS AND TEMPERATURES FOR TUESDAY INTO
WEDNESDAY BASED ON MODEL INCONSISTENCY. CHAMBERS
&&
.AVIATION...
MVFR CEILINGS WILL PERSIST THIS MORNING EAST OF ROSEBUD
COUNTY INCLUDING KMLS AND KBHK...SLOWLY CLEARING FROM WEST TO
EAST THIS AFTERNOON. OTHERWISE VFR CONDITIONS WILL PREVAIL TODAY.
A WEAK DISTURBANCE WILL BRING ISOLATED RAIN/SNOW SHOWERS TO THE
AREA THIS AFTERNOON INTO TONIGHT. CHAMBERS
&&
.PRELIMINARY POINT TEMP/POPS...
TDY THU FRI SAT SUN MON TUE
-------------------------------------------------------
BIL 043 027/044 028/051 036/058 039/046 037/040 025/043
0/B 21/B 11/B 00/U 12/W 53/J 11/B
LVM 039 024/040 028/044 032/052 035/043 031/036 022/041
1/N 22/W 12/J 00/B 14/W 43/J 22/J
HDN 042 024/042 024/048 032/056 036/052 038/039 026/042
0/U 21/B 10/B 00/U 12/W 54/J 11/B
MLS 044 028/046 030/049 036/056 038/055 038/038 028/041
1/B 21/B 10/B 00/B 11/B 44/J 21/E
4BQ 040 023/040 026/046 034/054 035/052 037/038 027/041
0/B 22/J 10/B 00/B 02/W 44/J 31/E
BHK 034 023/039 024/044 033/051 036/050 033/034 025/035
1/E 12/W 11/B 00/B 01/B 44/J 31/E
SHR 036 013/037 018/042 028/052 029/051 026/035 020/039
0/U 11/B 11/B 10/U 02/W 53/J 21/B
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
WY...NONE.
&&
$$
WEATHER.GOV/BILLINGS
AREA FORECAST DISCUSSION
NWS SIOUX FALLS SD
530 AM CST WED FEB 27 2013
.DISCUSSION.../ISSUED AT 308 AM CST/
A MOSTLY CLOUDY AND BREEZY DAY IS IN STORE FOR THE AREA. LOW CLOUDS
SEEM TO BE BREAKING UP OVER MUCH OF THE AREA...BUT MID AND HIGH
CLOUDS WILL REMAIN ABUNDANT. NORTHWESTERLY WINDS WILL INCREASE
THROUGH THE DAY...WITH GUSTS AROUND 30 MPH THIS AFTERNOON. STRONGEST
WINDS ARE ANTICIPATED ALONG THE MISSOURI RIVER...AND ACROSS PORTIONS
OF NORTHWEST IOWA AND SOUTHWEST MINNESOTA...WHERE WE COULD SEE GUSTS
UP TO 35 MPH. HIGHS WILL CONTINUE TO RUN A FEW DEGREES BELOW
NORMAL...WITH READINGS MAINLY IN THE LOW TO MID 30S. LOOKS LIKE
STRATUS WILL MOVE BACK INTO THE AREA LATER TODAY INTO TONIGHT FROM
NORTHWEST TO SOUTHEAST IN A WEAK COLD AIR ADVECTION REGIME. THESE
CLOUDS AND A CONTINUED NORTHERLY BREEZE SHOULD KEEP LOWS IN THE LOW
20S. LOW LEVEL MOISTURE EVENTUALLY BECOMES PRETTY DEEP BY LATER
TONIGHT INTO THURSDAY MORNING...SUGGESTING WE COULD END UP SEEING
SOME SCATTERED FLURRIES FROM THE LOW CLOUDS. AREA OF UPPER LEVEL
DIVQ IS ALSO OVERHEAD THURSDAY...BUT ENOUGH MID LEVEL DRY AIR
EXISTS...THAT FEEL ANY FLURRIES THAT DO FALL WILL BE LOW STRATUS
BASED...AND NOT FROM THE UPPER LEVEL FORCING...AND THE BEST THREAT
OF THIS WILL PROBABLY BE ALONG AND NORTH OF INTERSTATE 90. HIGHS
THURSDAY LIKELY A BIT COOLER THAN TODAY...MAINLY UPPER 20S TO LOW
30S.
SOME SIGNS THAT WE SEE A FRONTAL BAND OF SNOW ON THURSDAY NIGHT INTO
FRIDAY MORNING AS A WAVE AND SURFACE LOW DROPS SOUTHEAST. NAM IS
MOST AGGRESSIVE WITH THIS FEATURE...BUT THE GFS...SREF AND ECMWF ALL
HINTING AT SOMETHING. THUS WILL ADD IN A SLIGHT CHANCE OF SNOW WEST
OF THE JAMES RIVER...WHERE BEST THREAT APPEARS TO BE. OTHERWISE MUCH
OF THE SAME FRIDAY...WITH PARTLY TO MOSTLY CLOUDY SKIES AND HIGHS IN
THE MID 20S TO LOWER 30S. WEST COAST RIDGE TRIES TO BUILD EAST OVER
THE WEEKEND. QUITE THE DIFFERENCE BETWEEN THE GFS AND ECMWF ON HOW
FAR EAST THE RIDGE BUILDS...WITH AROUND A 10C DIFFERENCE IN MODEL
850MB TEMPERATURES...ECMWF BEING WARMER. GEM SEEMS TO BE BETWEEN THE
TWO...AND THUS WILL CONTINUE WITH VALUES CLOSE TO CONSENSUS THROUGH
THE WEEKEND. EVEN IF THE WARMER ECMWF VERIFIES...WARMING WILL LIKELY
BE TEMPERED BY SNOW COVER AND CLOUDINESS. FOR NOW HIGHS IN THE 20S
EAST TO 40S WEST SEEM MOST LIKELY.
ATTENTION WILL THEN TURN TO A WAVE COMING ASHORE ALONG THE PACIFIC
NORTHWEST COAST...WHICH WILL DIVE SOUTHEAST INTO THE PLAINS MONDAY
INTO MONDAY NIGHT. ECMWF AND GEM A BIT STRONGER WITH THIS WAVE AND
THUS A LITTLE FURTHER SOUTH. WILL HAVE TO CONTINUE TO MONITOR
TRENDS...BUT AT THIS TIME FAVOR A SOLUTION CLOSER TO THE GEM AND
ECMWF. THIS SYSTEM DOES HAVE SOME DECENT MOISTURE TO WORK WITH...SO
WHILE NOT EXPECTING ANYTHING TOO SIGNIFICANT...THINK AN AREA OF
ACCUMULATING SNOW IS PROBABLE TO THE NORTH OF THE LOW TRACK. IN FACT
THE ECMWF SHOWS A LARGE SWATH OF 0.4 TO 0.7 INCHES OF QPF IN A BAND
NORTH OF THE LOW TRACK. EVEN IF THIS IS OVERDONE...WOULD EXPECT AT
LEAST LIGHT SNOW ACCUMULATIONS...WITH POTENTIALLY A NARROWER AREA OF
MORE MODERATE AMOUNTS. AGAIN WHERE THIS OCCURS IS STILL
UNCERTAIN...AND IF THE SOUTHWARD TREND ON THE ECMWF WERE TO
CONTINUE...MOST OF THE SNOW COULD EVEN END UP SOUTHWEST OF OUR CWA.
EITHER WAY SOMETHING TO WATCH OVER THE COMING DAYS. PRECIP TYPE MAY
INITIALLY BE RAIN OR SNOW...BUT WITH THE SOUTHWARD TREND...EXPECTING
MAINLY SNOW WITH ANYTHING THAT ENDS UP FALLING. TEMPERATURES SHOULD
STAY A LITTLE BELOW NORMAL BEHIND THIS SYSTEM INTO EARLY NEXT WEEK.
/CHENARD
&&
.AVIATION.../FOR THE 12Z TAF ISSUANCE/
THE SIOUX FALLS FORECAST AREA HAS NOW LOST ALL STRATUS EXCEPT FOR A
NARROW STRIPE OF IFR EXTENDING FROM KYKN TO KSUX. THE STRATUS IN
THIS AREA CONTINUES TO BE OBSCURED ON THE IR SATELLITE BY ABUNDANT
HIGH LEVEL CLOUDINESS. BUT WITH LOW LEVEL WINDS FROM THE NORTH AND
NORTHWEST...IT IS LIKELY THAT DRIER AIR WILL ALSO ENTRAIN INTO THESE
AREAS SHORTLY...AND THUS GIVE THE KSUX TAF SITE VFR CONDITIONS BY
EARLY THIS MORNING. TO THE WEST OF OUR FORECAST AREA...PLENTY OF
MVFR STRATUS EXISTS IN CENTRAL SD AND ND. EVENTUALLY...THIS STRATUS
WILL BEGIN TO MOVE INTO OUR WESTERN ZONES. BUT IT MAY TAKE AWHILE AS
WINDS AT 925MB WILL REMAIN DUE NORTHERLY THROUGH THE MORNING HOURS
IN OUR FORECAST AREA. BOTH THE NAM12 AND RAP MODELS STRONGLY SUGGEST
THAT THE MVFR CEILINGS WILL NOT GET INTO THE KHON TAF SITE UNTIL
ABOUT 20Z. THIS AFTERNOON...THE 925MB WINDS DO INDEED BECOME MORE
NORTHWESTERLY AS OPPOSED TO NORTH...SO THIS MAKES SENSE AT THIS
TIME. EXTRAPOLATING THE STRATUS FURTHER EASTWARD...GIVES AN MVFR
ARRIVAL OF AROUND 00Z/28 FOR KFSD...AND ABOUT 02Z/28 FOR KSUX.
LASTLY...NORTHWEST SURFACE WINDS WILL BE RATHER BREEZY IN THE LATE
MORNING AND AFTERNOON AT 15 TO 25 KNOTS EAST OF THE JAMES RIVER
VALLEY. HOWEVER DUE TO A WELL MIXED DAY TODAY...THERE WILL LIKELY
NOT BE ANY VISIBILITY RESTRICTIONS TONIGHT BELOW THE VFR OR MVFR
CATEGORY. /MJF
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
&&
$$
YOU CAN SEE AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML.
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
500 PM CST THU FEB 28 2013
.SHORT TERM...TONIGHT THROUGH SATURDAY NIGHT
315 PM CST THU FEB 28 2013
AT 3 PM...CLOUDS CONTINUE TO PIVOT AROUND A LOW PRESSURE SYSTEM
CENTERED OVER SOUTHEAST ONTARIO. HOWEVER SOME DRIER AIR FILTERING
INTO NORTHERN MINNESOTA...UPPER MICHIGAN...AND NORTHERN WISCONSIN
IS CAUSING SOME BREAKS TO DEVELOP IN THE MVFR DECK. BUFKIT SOUNDINGS
SUGGEST THAT THE CLOUDS WILL LINGER ACROSS THE FORECAST AREA
TONIGHT...AND THEN GRADUALLY BREAK UP FROM NORTHEAST TO SOUTHWEST
ON FRIDAY. AT THE SAME TIME...SOME MID AND HIGH CLOUDS WILL BE
MOVING INTO THE AREA FROM THE WEST AS A WEAKENING SHORT WAVE
/CURRENTLY OVER THE DAKOTAS/ MOVES EAST TOWARD THE FORECAST AREA.
WITH SKIES EXPECTED TO REMAIN CLOUDY TONIGHT...ONCE AGAIN WENT
HIGHER THAN THE MAV AND MET MOS TEMPERATURES. A 50-50 BLEND
OF LAST NIGHT/S MINIMUM TEMPERATURES AND THE BIAS CORRECTED
CONSALL...RAISED THE MINIMUM TEMPERATURES INTO THE MID AND
UPPER TEENS ACROSS NORTH-CENTRAL WISCONSIN...AND LOWER AND MID 20S
ACROSS THE REMAINDER OF THE FORECAST AREA. THIS SEEMS MUCH MORE
REALISTIC THAN THE MOS.
ALSO FOR TONIGHT...A WEAK 850-700 MB WILL MOVE SOUTH THROUGH
THE AREA TONIGHT. IN ADDITION...THERE IS SOME WEAK 275 ISENTROPIC
LIFT. SOUNDINGS SUGGEST THAT THE OMEGA ASSOCIATED WITH THIS
FEATURE WILL BE CO-LOCATED WITH THE LOW LEVEL MOISTURE. AS A
RESULT...KEPT SCATTERED FLURRIES IN THE FORECAST.
ON SATURDAY NIGHT...THE MODELS SHOW THAT A WEAKENING TROUGH WILL
MOVE INTO THE UPPER LEVEL RIDGE. WEAK TO MODERATE 280K ISENTROPIC
LIFT DEVELOPS AHEAD OF THIS TROUGH. THE 28.00Z NAM/WRF CONTINUES
TO SHOW SOME LIGHT PRECIPITATION ASSOCIATED WITH THIS SYSTEM.
THE ECMWF GENERATES SOME FLURRIES WITH THIS SYSTEM. MEANWHILE THE
GEM AND OPERATIONAL GFS KEEPS THE AREA DRY. LOOKING AT THE 12 GFS
MEMBERS...ONLY 3 OF THEM GENERATE ANY MEASURABLE PRECIPITATION.
THE MAIN DIFFERENCE BETWEEN THE GFS AND NAM IN THE BUFKIT
SOUNDINGS IS HOW THEY HANDLE THE DRY AIR BELOW 5K FEET. THE
NAM/WRF SATURATES THIS LAYER. MEANWHILE THE GFS SHOWS THAT THIS
LAYER WILL REMAIN VERY DRY. WITH UNCERTAINTIES IN THE LOW LEVEL
MOISTURE...JUST OPTED TO GO WITH FLURRIES AT THIS TIME.
.LONG TERM...SUNDAY THROUGH THURSDAY
315 PM CST THU FEB 28 2013
FROM LATE SUNDAY NIGHT INTO TUESDAY...THE MAIN FORECAST CONCERN IS
THE TRACK OF A LOW PRESSURE SYSTEM MOVING THROUGH THE REGION. BOTH
THE GFS AND ECMWF HAVE SHIFTED THE TRACK OF THIS LOW EVEN FURTHER
SOUTH OF ITS TRACK AT 28.00Z AND 28.06Z. WITH THIS TRACK...IT
WOULD ONLY AFFECT SOUTHEAST MINNESOTA AND NORTHEAST IOWA. MEANWHILE
THE GEM KEEPS THE SYSTEM TRACKING TO OUR NORTH. WITH THIS
TRACK...IT CONTINUES TO PRODUCE PRECIPITATION ACROSS THE ENTIRE
AREA. WITH THE MODELS STILL TRYING TO SORT OUT THINGS...OPTED TO
STAY WILL ALL BLEND FOR NOW.
BEYOND THIS TIME PERIOD...IT CONTINUES TO LOOK LIKE A 500 MB RIDGE
WILL DEVELOP ACROSS THE CENTRAL UNITED STATES. AS STATED
YESTERDAY...THIS IS ACTUALLY SUPPORTED BY MADDEN JULIAN
OSCILLATIONS FOR PHASES 6 AND 7. WHILE THERE IS AGREEMENT THAT
THIS RIDGE WILL BE BUILDING ACROSS THE AREA...THERE IS STILL SOME
UNCERTAINTY ON HOW WARM WE WILL GET.
&&
.AVIATION...
500 PM CST THU FEB 28 2013
CLEARING OUT OF LOW STRATUS DECK PROBLEMATIC. LATEST RAP13/NAM12
WOULD SUGGEST THAT THE MOSTLY MVFR CIGS WOULD NOT SINK SOUTH OF THE
TAF SITES UNTIL 12Z OR SO. SOME SUPPORT OF FOG/STRATUS SATELLITE
TRENDS FOR THIS. RAP BUFKIT SOUNDINGS HANG ONTO A LOT MORE MOISTURE
THOUGH...KEEPING THE ATMOSPHERE SATURATED SUB A 900 MB INVERSION
THROUGH AT LEAST 14Z. FORECAST CONFIDENCE REMAINS SHAKY ON JUST WHEN
IT WILL CLEAR...BUT SOUNDINGS AT LEAST SUGGEST MORE MIXING TO AID IN
DISSIPATING THE LOW LEVEL MOISTURE FRI MORNING. WILL CONTINUE TO
DELAY THE CLEARING BASED ON MESO MODELS/SATELLITE TRENDS. HIGH
CLOUDS WILL LIKELY BE FILTERING BACK ACROSS THE REGION EVEN AS THE
LOW CLOUDS VACATE TO THE SOUTH...ASSOCIATED WITH A WEAK UPPER LEVEL
DISTURBANCE.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
228 PM CST THU FEB 28 2013
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...BOYNE
LONG TERM....BOYNE
AVIATION.....RIECK
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
322 PM CST WED FEB 27 2013
.SHORT TERM...TONIGHT THROUGH FRIDAY NIGHT
321 PM CST WED FEB 27 2013
AT 3 PM...A LOW PRESSURE SYSTEM WAS LOCATED ACROSS SOUTHERN LOWER
MICHIGAN. CYCLONIC FLOW AROUND THIS LOW HAS KEPT CLOUDS AND LIGHT
SNOW ACROSS MUCH OF THE FORECAST AREA TODAY.
FOR TONIGHT...THE 27.00Z MODELS ARE IN GOOD AGREEMENT THAT A
SHORT WAVE ROTATING AROUND THE UPPER LEVEL LOW WILL MOVE WEST
SOUTHWEST ACROSS AREA THIS EVENING. THIS SYSTEM WILL PRODUCE
AROUND 4 MICROBAR/SEC OF OMEGA BELOW 10K FEET THIS EVENING. THIS
LIFT IS CO-LOCATED WITH THE DEEP MOISTURE. THE DEEPEST LIFT IS
FOUND ACROSS EASTERN AND SOUTHERN PORTIONS OF THE FORECAST AREA.
AS A RESULT...RAISED THE PRECIPITATION PROBABILITIES TO
90 PERCENT IN THESE AREAS. SOUNDINGS ARE COLD ENOUGH THAT THE
PRECIPITATION WILL BE IN THE FORM OF SNOW. UNLIKE THIS
AFTERNOON WHERE THE SNOW HAD A HARD TIME ACCUMULATING DUE TO THE
HIGH SOLAR ANGLE...EXPECT SOME LIGHT ACCUMULATIONS /UP TO A HALF
INCH/ TO OCCUR THIS EVENING.
WITH CLOUDS REMAINING ACROSS THE REGION AND NO COLD AIR ADVECTION
COMING INTO THE AREA...STAYED CLOSE TO THE LOW TEMPERATURES WHICH
OCCURRED THIS MORNING.
ON THURSDAY...THE CYCLONIC FLOW REMAINS ACROSS THE REGION. THE
BUFKIT SOUNDINGS CONTINUE TO SHOW SOME WEAK OMEGA BELOW 5K. DUE TO
THIS...INTRODUCED FLURRIES TO THE FORECAST. THIS LIFT MAY BE UNDER
DONE IN THE MODELS BECAUSE THERE APPEARS TO BE A WEAK SHORT WAVE
IN THE 700 AND 500 MB WIND FIELDS. IF THIS IS THE CASE...THE
PRECIPITATION CHANCES WILL LIKELY HAVE TO BE INCREASED.
FROM THURSDAY NIGHT INTO FRIDAY NIGHT...HIGH PRESSURE WILL PROVIDE DRY
WEATHER. TEMPERATURES WILL AVERAGE A FEW DEGREES BELOW NORMAL.
.LONG TERM...SATURDAY THROUGH WEDNESDAY
321 PM CST WED FEB 27 2013
A WEAK TO MODERATE STRATOSPHERIC WARMING EVENT IN THE GULF OF
ALASKA WILL HELP THE ARCTIC OSCILLATION TO BECOME INCREASING
NEGATIVE /DROPPING TO -4/ THROUGH EARLY NEXT WEEK. AS A RESULT...
THE 500 MB FLOW PATTERN WILL BE A POSITIVE PACIFIC NORTH AMERICAN
/PNA/ TELECONNECTION. THIS WILL KEEP OUR AREA IN NORTHWEST FLOW
THROUGH AT LEAST TUESDAY. THE COLDEST 850 MB ANOMALIES /-3.5
STANDARD DEVIATIONS/ ASSOCIATED WITH THE EASTERN TROUGH WILL BE
FOUND ACROSS THE SOUTHEAST UNITED STATES. MEANWHILE IN OUR
AREA...THE 850 MB TEMPERATURE ANOMALIES ARE JUST A BIT BELOW
NORMAL.
FROM MONDAY INTO MONDAY NIGHT...THE 27.12Z GEM...GFS...AND ECMWF
ARE COMING TO SOME CONSENSUS THAT A LOW PRESSURE SYSTEM WILL MOVE
SOUTHEAST ACROSS THE DAKOTAS AND IOWA. THIS TRACK WOULD BRING SOME
SNOW TO THE AREA. THIS SYSTEM HAS BEEN FAIRLY CONSISTENT IN THE
GFS FOR THE PAST 3 RUNS. MEANWHILE THE ECMWF HAS SHOWED VERY
LITTLE RUN TO RUN CONSISTENCY. DUE TO THE GFS CONSISTENCY...
TRENDED THE FORECAST TOWARD IT AND RAISED THE PRECIPITATION
PROBABILITIES ABOUT 10 TO 20 PERCENT OVER THE ALL BLEND.
BEYOND THIS TIME PERIOD...THE ARE SIGNS IN BOTH THE GFS AND ECMWF
THAT THE 500 MB PATTERN WILL MAKE A DRAMATIC SHIFT IN THE 500 MB
PATTERN AS A STRONG 500 MB RIDGE DEVELOPS ACROSS THE CENTRAL
UNITED STATES. THE ECMWF HAS A MUCH STRONGER RIDGE THAN THE GFS. AS A
RESULT...ITS 850 MB TEMPERATURE ANOMALIES ARE STANDARD DEVIATION
ARE UP TO 2 ACROSS THE DAKOTAS BY WEDNESDAY. THERE IS ACTUALLY
SUPPORT FOR IN THE PACIFIC AS THE MADDEN JULIAN OSCILLATION MOVES
FROM PHASE 6 TO PHASE 7. BOTH OF THESE PHASES...SUPPORT WARMTH
ACROSS THE EASTERN HALF OF THE CONUS.
&&
.AVIATION...THROUGH 18Z THURSDAY
1142 AM CST WED FEB 27 2013
MAIN AVIATION CONCERNS ARE MVFR CONDITIONS AT BOTH TAF SITES AND
BREEZY NORTHERLY WINDS AT RST THROUGH TAF PERIOD. LATEST WATER
VAPOR SATELLITE IMAGERY INDICATING SEVERAL SHORTWAVE TROUGHS
ROTATING AROUND UPPER LEVEL LOW PRESSURE OVER THE OHIO RIVER
VALLEY. THE UPPER LEVEL LOW IS EXPECTED TO CONTINUE TO ROTATE LOW LEVEL
MOISTURE INTO THE REGION...ESPECIALLY INTO TONIGHT. LATEST 17Z METARS
INDICATE MVFR CONDITIONS AT BOTH RST AND LSE TAF SITES. THE
LATEST 27.12Z NAM AND 27.15Z RAP SHOW LOW LEVEL MOISTURE TO
SLOWLY DIMINISH OUT OF THE REGION AFTER 12Z THURSDAY.
HOWEVER...WITH REGION UNDER THE INFLUENCE OF THE UPPER LEVEL LOW
OVER THE OHIO RIVER VALLEY...CONFIDENCE IS NOT VERY HIGH THE TAF
SITES WILL COMPLETELY CLEAR OUT OF BROKEN CEILINGS/MVFR CONDITIONS BY 12Z
THURSDAY. HAVE KEPT MVFR CONDITIONS THROUGH THE TAF PERIOD. TIGHT
PRESSURE GRADIENT ON BACKSIDE OF SURFACE LOW OVER SOUTHERN
MICHIGAN WILL ALLOW SUSTAINED WIND SPEEDS OF 15 TO 18 KNOTS AND
GUST 20 TO 25 KNOTS AT RST THROUGH 03Z THURSDAY.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
321 PM CST WED FEB 27 2013
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...BOYNE
LONG TERM...BOYNE
AVIATION...DTJ
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
1142 AM CST WED FEB 27 2013
.SHORT TERM...
1142 AM CST WED FEB 27 2013
LATEST RADAR TRENDS HAVE SHOWN SNOW BANDS WEAKENING AND MOVING
OUT OF THE ADVISORY AREA. WITH TEMPERATURES WARMING INTO THE LOWER
TO MIDDLE 30S OVER THE SOUTHWEST WISCONSIN AND NORTHEAST
IOWA...WILL MITIGATE ANY SNOWFALL ACCUMULATION ON ROADWAYS THIS
AFTERNOON. THEREFORE...WILL LET THE WINTER WEATHER ADVISORY EXPIRE
AT NOON TODAY FOR SOUTHWEST WISCONSIN AND NORTHEAST IOWA.
.LONG TERM...SATURDAY THROUGH TUESDAY
306 AM CST WED FEB 27 2013
MEDIUM RANGE MODEL RUNS OF 27.00Z IN REASONABLE AGREEMENT WITH EACH
OTHER AND THEIR PREVIOUS RUNS FOR THE AREA TO BE UNDER NORTHWEST TO
NORTH FLOW ALOFT THRU THE WEEKEND AND BULK OF ANY SHORTWAVE ENERGY
DROPPING THRU THE FLOW REMAINING WEST OF THE AREA. FCST FOR SAT/SUN
REMAINS DRY WITH TEMPS A CATEGORY OR TWO BELOW THE NORMALS AS MARCH
BEGINS. BETWEEN MODEL CONSISTENCY IMPROVING FOR MON/TUE WITH
BREAKDOWN OF THE WESTERN NOAM RIDGE AS A RATHER STRONG SHORTWAVE
MOVES THRU THE NORTHERN ROCKIES SUN THEN ACROSS THE CENTRAL PLAINS
MON INTO THE MID MS VALLEY TUE. THIS TRENDS SOUTH/WEST WITH THE
SHORTWAVE FROM THE EARLIER RUNS. MODEL CONSENSUS CONTINUES A -SN
CHANCE ACROSS MUCH OF THE AREA MON INTO TUE BUT CONFIDENCE FOR THIS
ON DAYS 6/7 NOT HIGH GIVEN THE TREND/SHIFT OF THE SHORTWAVE ENERGY
TO THE SOUTHWEST. IF THE TREND CONTINUES FOR ANOTHER CYCLE...APPEARS
MON-TUE WILL NEED TO BE SHIFTED TO A DRY FCST. NOT A LOT OF
CONFIDENCE IN THE DAY 6/7 PERIOD AT THIS TIME AND LEFT THE 27.00Z
MODEL/ENSEMBLE CONSENSUS DATA IN THE FCST GRIDS AS IS FOR NOW. WITH
A SHIFT BACK TO A MORE WESTERLY FLOW FOR EARLY NEXT WEEK...TEMPS
RETURNING TO NEAR NORMAL FOR MON/TUE LOOK WELL TRENDED.
&&
.AVIATION...THROUGH 18Z THURSDAY
1142 AM CST WED FEB 27 2013
MAIN AVIATION CONCERNS ARE MVFR CONDITIONS AT BOTH TAF SITES AND
BREEZY NORTHERLY WINDS AT RST THROUGH TAF PERIOD. LATEST WATER
VAPOR SATELLITE IMAGERY INDICATING SEVERAL SHORTWAVE TROUGHS
ROTATING AROUND UPPER LEVEL LOW PRESSURE OVER THE OHIO RIVER
VALLEY. THE UPPER LEVEL LOW IS EXPECTED TO CONTINUE TO ROTATE LOW LEVEL
MOISTURE INTO THE REGION...ESPECIALLY INTO TONIGHT. LATEST 17Z METARS
INDICATE MVFR CONDITIONS AT BOTH RST AND LSE TAF SITES. THE
LATEST 27.12Z NAM AND 27.15Z RAP SHOW LOW LEVEL MOISTURE TO
SLOWLY DIMINISH OUT OF THE REGION AFTER 12Z THURSDAY.
HOWEVER...WITH REGION UNDER THE INFLUENCE OF THE UPPER LEVEL LOW
OVER THE OHIO RIVER VALLEY...CONFIDENCE IS NOT VERY HIGH THE TAF
SITES WILL COMPLETELY CLEAR OUT OF BROKEN CEILINGS/MVFR CONDITIONS BY 12Z
THURSDAY. HAVE KEPT MVFR CONDITIONS THROUGH THE TAF PERIOD. TIGHT
PRESSURE GRADIENT ON BACKSIDE OF SURFACE LOW OVER SOUTHERN
MICHIGAN WILL ALLOW SUSTAINED WIND SPEEDS OF 15 TO 18 KNOTS AND
GUST 20 TO 25 KNOTS AT RST THROUGH 03Z THURSDAY.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
1142 AM CST WED FEB 27 2013
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...DTJ
LONG TERM....RRS
AVIATION...DTJ
AREA FORECAST DISCUSSION...UPDATED
NWS MILWAUKEE/SULLIVAN WI
1102 PM CST TUE FEB 26 2013
.UPDATE...
ADDED FOND DU LAC AND WASHINGTON COUNTIES TO WARNING AS PERSISTENT
SNOW BAND LINGERS WITH CALLS TO THE SHERIFF DEPARTMENTS INDICATING
THE FALLING SNOW AND GUSTY WINDS WERE MAKING ROADS NEARLY
IMPASSIBLE IN EASTERN FOND DU LAC COUNTY AND NORTHERN WASHINGTON.
HEAVIER SNOW BANDS NOT MAKING A LOT OF PROGRESS TO THE WEST AS
DRIER AIR...MARKED BY LOWER DEW POINTS...IS NOSING INTO NW
PORTIONS OF THE FORECAST AREA.
ALSO WATCHING THE FIRST OF NUMEROUS SNOW SHOWERS MOVING ONSHORE
OVER EXTREME NE IL/SE WI. WAUKEGAN IL DOWN TO 3/4 MILE...OR 1/2
INCH/HOUR SNOW RATE...WITH THIS LEAD SNOW SHOWER BAND.
&&
.AVIATION/06Z TAFS/...
WILL LIKELY KEEP TAF SITES AT IFR LEVELS...ESPECIALLY CIGS...THROUGH
THE FORECAST PERIOD ...THOUGH GFS GUIDANCE INDICATES KMSN MAY
IMPROVE TO MVFR EARLY WEDNESDAY EVENING IN SUBSIDENCE BEHIND
SPOKE OF VORTICITY ROTATING AROUND UPPER LOW. EXPECT STEADY
ACCUMULATING SNOW TO BECOME MORE OCCASIONAL THROUGH THE OVERNIGHT
AS FORM OF PRECIPITATION TURNS TO SNOW SHOWERS...WITH BREAKS
BETWEEN CELLS. NORTHEAST WINDS WILL TURN NORTH BUT REMAIN
GUSTY...WITH THE STRONGEST WINDS AT KMKE AND KENW...EASING SLOWLY
TO THE WEST AT KUES AND KMSN.
&&
.MARINE...
WILL BE EXTENDING GALE WARNING UNTIL 09Z AS BOTH RAP AND NAM
SOUNDINGS TAP 37 KNOT+ WINDS UNTIL AT LEAST 08Z. NOT SEEING GALE
GUSTS AT SOUTHERN LOCATIONS AT THIS TIME...BUT GRADIENT WILL
TIGHTEN FOR A TIME AS LOW LIFTS TOWARD SRN LOWER MICHIGAN AND
WINDS BECOME NORTH.
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...WINTER STORM WARNING UNTIL NOON CST WEDNESDAY FOR WIZ051-052-059-
060-066-070>072.
WINTER WEATHER ADVISORY UNTIL NOON CST WEDNESDAY FOR WIZ058-
062>065-067>069.
LM...GALE WARNING UNTIL 3 AM CST WEDNESDAY FOR LMZ643>646.
&&
$$
UPDATE...REM
TONIGHT/WEDNESDAY AND AVIATION/MARINE...MEB
WEDNESDAY NIGHT THROUGH TUESDAY...DAVIS
AREA FORECAST DISCUSSION
NWS DENVER/BOULDER CO
1001 PM MST THU FEB 28 2013
.UPDATE...
&&
.SHORT TERM...SWIFT NORTH-NORTHWEST FLOW ALOFT IN PLACE. A WEAK
UPPER AIR PERTURBATION IN THIS FLOW CURRENTLY PASSING OVER COLORADO.
DISTURBANCE WAS GENERATING ONLY WEAK MID/UPPER LEVEL QG ASCENT.
CLOUD COVER AND LIGHT SNOWFALL IN THE NORTHERN MOUNTAINS PRINCIPALLY
THE PRODUCT OF OROGRAPHICS...I.E. NORTHERLY UPSLOPE FLOW. 1 TO 3
INCH SNOW ACCUMULATIONS STILL LOOKS GOOD FOR THE NORTHERN MTNS
OVERNIGHT. 25-40KTS NWLY WINDS ON THE MTN TOPS AND HIGH PASSES ALSO
PRODUCING AREAS OF BLOWING/DRIFTING SNOW. LIKELY WE/LL SEE THIS
CONTINUE IN THESE HIGH TERRAIN AREAS REST OF TONIGHT AS WINDS ALOFT
ASSUME MORE OF A NORTHERLY COMPONENT. EAST OF THE MOUNTAINS...SNOW
CHANCES PRETTY MUCH OVER...EXCEPT PERHAPS ALONG THE PALMER DIVIDE IN
ELBERT AND NORTHERN LINCOLN COUNTIES...OUT ACROSS ERN PORTIONS OFF
ADAMS AND ARAPAHOE COUNTIES AND SOUTHERN WASHINGTON OVER THE NEXT 2-
4 HRS. NO ACCUMULATION AND ANY SNOWFALL WILL BE QUITE LIGHT AS SUB-
CLOUD LAYER IS QUITE DRY. COUNTING ON CLEARING UP ALONG THE WYOMING
BORDER AFTER MIDNIGHT...WITH PARTIAL CLEARING ALONG THE FRONT RANGE
BEFORE MORNING LIGHT.
.AVIATION...VFR CONDITIONS TO CONTINUE IN THE DENVER METRO AREA
NEXT 24 HOURS. SNOW CHANCES ALMOST NIL REST OF TONIGHT. SOUTH-
SOUTHEAST WINDS OF 5-12KTS IN THE DENVER METRO AREA MAY GO
NORTHWESTERLY 5-10KTS FOR A TIME AROUND MIDNIGHT WITH OUTFLOW FROM
THE LAST OF THE SNOW SHOWERS ON THE HIGH FOOTHILLS. SKIES SHOULD
PARTIALLY CLEAR OVER THE METRO AREA DURING THE PRE-DAWN HOURS.
&&
.PREV DISCUSSION... /ISSUED 349 PM MST THU FEB 28 2013/
SHORT TERM...MOISTURE CONTINUES TO INCREASE ACROSS MOUNTAINS AS
DISTURBANCE BEGINS TO MOVE INTO WESTERN COLORADO. MODERATE
NORTHWEST FLOW ALOFT PROVIDING DECENT OROGRAPHICS WITH OROGRAPHICS
AROUND 6 C/KM. MOUNTAIN WEB CAMS SHOWING SNOW SHOWERS BECOMING
MORE WIDESPREAD...MAINLY ALONG CONTINENTAL DIVIDE OF SUMMIT AND
GRAND COUNTIES AS WELL AS PARK AND GORE RANGES OF WESTERN JACKSON
COUNTY. SO FAR... ACCUMULATIONS MINIMAL BASED ON LATEST SNOTEL
DATA. WINDS HAVE BEEN GUSTY OVER THE HIGHER MOUNTAINS AND ALONG
FOOTHILLS AS WELL AS ACROSS SOUTH PARK. DISTURBANCE TO MOVE ACROSS
MOUNTAINS AND PLAINS THROUGH THE EVENING. LATEST RAP AND NAM QG
VERTICAL VELOCITY PROGS STILL INDICATING ASCENT TO BE MINIMAL...SO
MOUNTAIN SNOWFALL TO BE MAINLY OROGRAPHICALLY DRIVEN WITH SOME
HELP WITH INSTABILITY. ACCUMULATIONS OF 1 TO 4 INCHES STILL
LOOKING ON TRACK THOUGH SOME LOCATIONS ALONG THE FAVORED WEST AND
NORTHWEST ASPECTS COULD RECEIVE A COUPLE EXTRA INCHES. NORTHWEST
FLOW TO PROVIDE DOWNSLOPE IN AND NEAR FOOTHILLS SO SNOW SHOWERS
THERE WILL BE LIMITED. BUT THERE WILL BE SOME WIND GUSTS TO 50 MPH
DUE TO THE DOWNSLOPE. ACROSS PLAINS... SOUTHEAST WINDS DEVELOPED
IN THE DENVER AREA DUE TO WEAK ANTICYCLONE OVER SOUTHERN WELD
COUNTY. LATEST MODELS SHOWING THIS ANTICYCLONE SHIFTING EAST OF
THE DENVER AREA DURING THE EVENING AS DOWNSLOPE OFF FOOTHILLS
BEGINS TO DOMINATE FRONT RANGE. STILL THINKING THIS DOWNSLOPE FLOW
WILL LIMIT SNOW CHANCES ALONG URBAN CORRIDOR. MODELS STILL SHOWING
BEST CHANCE FOR SHOWERS TO BE EAST AND SOUTH OF DENVER...PAINTING
SOME LIGHT QPF AND SNOW ACCUMULATIONS. WILL UP THE POPS TO THE
CHANCE CATEGORY IN THIS AREA...KEEPING REST OF THE POPS AS IS.
LATEST CROSS SECTIONS INDICATE A GRADUAL DECREASE IN MOISTURE
AFTER MIDNIGHT. STILL GOOD OROGRAPHICS FOR CONTINUED MOUNTAIN SNOW
SHOWERS. CLOUD COVER AND WIND TO HELP MODERATE OVERNIGHT
TEMPERATURES. ON FRIDAY...FLOW ALOFT BECOMES A BIT MORE NORTHERLY
AS TROUGH MOVES INTO CENTRAL PLAINS. MOISTURE OVER MOUNTAINS
CONTINUES TO DRY OUT. OROGRAPHICS STILL FAVORABLE FOR MOUNTAIN
SNOW SHOWERS...THOUGH INCREASING STABILITY AND LACK OF LIFT WILL
LIMIT COVERAGE. PERHAPS ANOTHER INCH OR SO OF ACCUMULATION. ACROSS
PLAINS...SOME MID AND HIGH LEVEL CLOUDS TO PREVAIL. AIRMASS TO
WARM SLIGHTLY...SHOULD ALLOW TEMPERATURES TO WARM INTO THE 40S
ACROSS THE PLAINS...THOUGH SNOW COVER COULD KEEP TEMPERATURES IN
THE 30S. WINDS TO BE A BIT GUSTY ACROSS HIGHER RIDGES AND FAR
EASTERN PLAINS.
LONG TERM...THE CWA WILL BE UNDER FAIRLY STRONG NORTHERLY FLOW
ALOFT BY FRIDAY EVENING AS A VERY FAST MOVING SHORT WAVE TROUGH
WHICH CLIPS THE HIGH PLAINS STATES EARLY FRIDAY MOVES OUT OF THE
AREA. THE 12Z NAM INDICATES A SECOND BUT VERY MINOR DISTURBANCE IN
THE NORTHERLY FLOW WHICH PROVIDES ADDITIONAL BUT SCANT MOISTURE TO
THE HIGH COUNTRY ALONG WITH ANOTHER PUSH OF STRONG NORTHWEST WINDS
ACROSS THE NORTHEAST PLAINS LATE FRIDAY INTO EARLY SATURDAY. DRY
DOWNSLOPE LOOKS TO BE THE RULE ONCE AGAIN WITH NO POPS EXPECTEDAT
LOWER ELEVATIONS. IN THE HIGH COUNTRY...CROSS SECTIONS CONTINUE TO
SHOW SHALLOW MOISTURE BEING HELD AGAINST THE DIVIDE WITH
OROGRAPHICS DOING THE ONLY LIFTING FOR ANY SNOW SHOWERS. GFS-QG
FIELDS INDICATE NEUTRAL TO SLIGHT DOWNWARD MOTION FRIDAY EVE
THROUGH LATE SATURDAY AND SEE NO REASON TO BUMP THE POPS OVER THE
ISOLD SNOW SHOWERS CURRENTLY IN THE ZFP. BY MIDDAY/EVE SATURDAY
THE AMPLIFIED RIDGE OF HIGH PRESSURE WITH AN AXIS LOCATED OVER THE
EASTERN EDGE OF THE GREAT BASIN IS ALREADY WEAKENING OUT AHEAD OF
THE NEXT DISTURBANCE EXPECTED FOR THE NORTHERN COLO EARLY SUNDAY.
AS THE WEAKENING RIDGE MOVES OUT OVER THE CENTRAL US...TIGHT
PACKING IN THE MID/UPPER LEVEL HEIGHT FIELDS PROVIDES FOR SOME
BRIEF BUT STRONG WESTERLY FLOW ACROSS THE STATE ON SUNDAY.
SANGSTER HIGH WIND MODEL INDICATES POTENTIAL HIGH WIND CRITERIA
BEING MET FOR THE SUNDAY AFT/EVE. WILL BUMP UP WIND GRIDS FOR THIS
NOTIFICATION AND SHD BE WATCHED IN LATER RUNS. AFTER THIS
INFLECTION POINT IN THE FLOW ALOFT...LATEST GFS/CMC TRAJECTORY
WITH THIS NEXT FAST MOVING WAVE TAKES UPPER LOW OVER WESTERN MT
SOUTHEASTWARD OVER THE BLACK HILLS REGION OF SD AND INTO EAST CENT
NE BY MONDAY NIGHT. THIS WILL DO MUCH LIKE THE PREVIOUS WAVES
GIVING A BRIEF SHOT OF LIGHT SNOW TO THE NORTHERN AND CENT MTNS
WHILE PRODUCING DRY NORTHWEST DOWNSLOPE FLOW EAST OF THE DIVIDE.
ECM IS SLOWER WITH THE FEATURE BUT DRYER AND MORE NORTHERLY.
HOWEVER...HAVE ADJUSTED POP GRIDS AROUND THIS SUNDAY INTO EARLY
MONDAY TIME FRAME FOR THE MTN LOCATIONS FOR A LONGER PERIOD OF
LIGHT SNOW ASSOC WITH TROUGH.
LOOKING TOWARD THE TUESDAY THROUGH THURSDAY PERIOD...A WARM
STABLE RIDGE OF HIGH PRESSURE WILL CONTINUE TO DEVELOP OVER THE
WESTERN US WHILE MAXIMIZING IN THE TUESDAY EVENING TO EARLY
WEDNESDAY TIMEFRAME. WILL EXPECT TUE TO REMAIN COOL AND BREEZY IN
THE MORNING POST TROUGH THEN GOOD WARMING INTO TUESDAY AFTN AND THE
DAYS AHEAD. THIS RIDGE WILL LIKELY TAKE DAYTIME HIGHS WELL ABOVE
SEASONAL NORMALS AT LOWER ELEVATIONS FOR BOTH WED AND THURS AS
WARMER SOUTHWESTERLY FLOW ALOFT PREVAILS BOTH DAYS IN ADVANCE OF THE
NEXT LARGER AND COLDER WAVE BEYOND THURSDAY.
AVIATION...WEAK ANTICYCLONE NORTH OF DENVER...WITH SOUTHEAST
WINDS AT KDEN WHILE DOWNSLOPE WESTERLIES PREVAILING AT KBJC AND
KAPA. ANTICYCLONE EXPECTED TO MOVE SOUTHEAST OF DENVER DURING THE
EVENING...WITH WINDS SHIFTING TO THE NORTHWEST AT KDEN. CEILINGS
TO LOWER DURING THE EVENING...SHOULD REMAIN ABOVE 10000 FEET WITH
VFR CONDITIONS PREVAILING. SLIGHT CHANCE OF SNOW SHOWERS THIS
EVENING AS DISTURBANCE MOVES ACROSS. STILL THINKING THE BEST
CHANCE FOR SHOWERS WILL BE SOUTHEAST OF DENVER AS THE DOWNSLOPE
WIND SHOULD LIMIT THE SHOWERS. IF A SHOWER DOES OCCUR...IT SHOULD
BE LIGHT AND BRIEF WITH LITTLE OR NO ACCUMULATION. CEILINGS OF
AROUND 6000 FEET AGL COULD ACCOMPANY THE SHOWERS. FOR NOW WILL
LEAVE OUT OF THE TAFS. AFTER MIDNIGHT... WINDS TO SHIFT TO SOUTH
SOUTHWEST AS DRAINAGE DEVELOPS. SOUTHERLY WINDS TO PREVAIL THROUGH
THE DAY FRIDAY WITH SPEEDS LESS THAN 8 KTS. VFR TO CONTINUE.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...BAKER
LONG TERM....FREDIN
AVIATION...BAKER
AREA FORECAST DISCUSSION
NWS ALBANY NY
1245 AM EST FRI MAR 1 2013
.SYNOPSIS...
LOW PRESSURE WILL CONTINUE TO MOVE VERY SLOWLY OVER NEW YORK AND NEW
ENGLAND OVERNIGHT INTO FRIDAY. THE UPPER LOW WILL BRING CLOUDY
CONDITIONS AND NUISANCE LIGHT RAIN OR SNOW SHOWERS INTO THE WEEKEND.
TEMPERATURES WILL RUN SLIGHTLY ABOVE NORMAL THROUGH THE WEEKEND.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
AS OF 1245 AM EST...RADAR INDICATED THAT LIGHT PRECIPITATION HAS
FLARED UP IN THE HUDSON VALLEY...IN THE CAPITAL DISTRICT AND POINTS
NORTHWARD. LOOKS TO BE TIED INTO THE TERRAIN...BUT IRONICALLY AT
THIS TIME...LESS GOING ON ACROSS THE HIGHER TERRAIN THAN IN THE
MOHAWK VALLEY. MIGHT BE A FORM OF MOHAWK HUDSON CONVERGENCE SINCE
THE WIND HAS WEST IN THE MOHAWK VALLEY...NW AT KALB AND MORE
NORTHERLY AT KGFL. WHILE CERTAINLY NOT A PURE CASE...THERE IS
CLEARLY SOME SORT OF ENHANCEMENT IN OUR AREA.
THE LATEST NAM AND HRRR ACTUALLY INDICATED THIS ENHANCEMENT TO
HAPPEN. FOLLOWING IT CUE...AS THE CENTER OF THE UPPER AIR LOW LIFTS
A LITTLE NORTHEAST...SOMEWHAT DRIER SHOULD MOVE IN FROM THE SOUTH...
LIMITING ADDITIONAL SHOWERS BY PROBABLY UNTIL AFTER DAWN.
FOR THIS UPDATED...INCREASED POPS TO LIKELY ACROSS THE CAPITAL
DISTRICT FOR A FEW HOURS OVERNIGHT...SCATTERED MOST OTHER
PLACES...EXCEPT ISOLATED MID HUDSON VALLEY AND LOWER LITCHFIELD.
STILL WARM ENOUGH IN THE LOWEST LEVELS FOR THIS TO BE RAIN...AT
LEAST IN THE VALLEYS. THE FREEZING LAYER LOOKS TO BE AROUND 1500
FEET...MAYBE DROPPING A LITTLE BY DAWN. RAIN SHOWERS COULD CERTAINLY
MIX WITH WET SNOW FLAKES BY DAWN WITH NO ACCUMULATIONS EXPECTED.
HIGHER TERRAIN SURROUNDING THE CAPITAL REGION COULD RECEIVE UP TO AN
INCH OF PRECIPITATION.
DID NOT TINKER WITH OVERNIGHT LOWS...THEY LOOK IN THE BALL PARK.
WITH CLOUDS AND A LIGHT BREEZE IN PLACE...TEMPS WILL DROP
TONIGHT...BUT WILL NOT FREE FALL TOO MUCH. MIN TEMPS WILL RANGE FROM
NEAR 20 IN THE ADIRONDACKS TO NEAR 30 IN THE CAPITAL REGION/MID
HUDSON VALLEY.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH SUNDAY/...
FRIDAY...A REDUNDANT FORECAST WILL BE OCCURRING WITH THE STACKED
LOW...AS IT SLOWLY RETROGRADES EASTWARD OVER ERN NY AND NEW
ENGLAND. ANOTHER SPOKE OF VORTICITY ROTATING AROUND THE CUTOFF IN
THE CYCLONIC FLOW MAY FOCUS ISOLD-SCT RAIN AND SNOW SHOWERS AGAIN.
CHC AND LIKELY POPS WERE USED NORTH AND WEST OF THE CAPITAL
REGION. THE BEST CHC FOR SNOW SHOWERS WILL BE AT ELEVATIONS
GREATER THAN 1500 FT. LIGHT ACCUMULATIONS OF A COATING TO A HALF
AN INCH WILL BE POSSIBLE. ISOLD-SCT LIGHT RAIN SHOWERS WILL BE
POSSIBLE ELSEWHERE. THE MID HUDSON VALLEY...AND NW CT WILL LIKELY
REMAIN DRY. MAX TEMPS CLOSER TO A BLEND OF THE GFSMOS AND NAMMOS
GUIDANCE WERE USED WITH HIGHS IN THE U30S TO L40S IN THE
VALLEYS...AND GENERALLY U20S TO M30S OVER THE MTNS.
FRI NIGHT...THE CUTOFF LOW STARTS TO BECOME STRETCHED AND
ELONGATED OVER THE NORTHEAST. THE NAM/GFS HAS ANOTHER LOBE OF
VORTICITY MOVING ACROSS THE REGION TAPPING INTO SOME LOW OR MID
LEVEL MOISTURE. A SLIGHT TO LOW CHC OF SNOW SHOWERS IS LIKELY
AGAIN FROM THE CAPITAL REGION NORTH AND WEST. AGAIN...LIGHT SNOW
ACCUMS ARE POSSIBLE OF A COATING TO LESS THAN AN INCH. LOWS ARE
EXPECTED TO BE IN THE LOWER TO M20S WITH SOME TEENS OVER THE SRN
DACKS.
SAT-SUN...THE CUTOFF UPPER LOW CONTINUES TO PLAGUE NY AND NEW
ENGLAND WITH CLOUDS...AND A LOW RISK OF RAIN AND SNOW SHOWERS. THE
NAM/CANADIAN GUIDANCE INDICATES MORE THAN THE GFS THAT A STRONG
VORT MAX ROTATING AROUND THE CUTOFF UPPER LOW HIGH CHANCES OF
RAIN/SNOW SHOWERS LATE SAT INTO SAT NIGHT/SUNDAY MORNING. THE
COLUMN WILL DEFINITELY BE COLD ENOUGH FOR MORE SNOW THAN RAIN. THE
MOISTURE IS LIMITED UTILIZED BY THE CYCLONIC VORTICITY ADVECTION.
WE USED NO POPS OR SLIGHT CHC POPS IN THE HUDSON RIVER VALLEY ON
SAT...AND HIGH CHC OR LIKELY POPS OVER THE WRN DACKS...NRN
CATSKILLS...SRN GREENS AND BERKS. SAT NIGHT INTO SUNDAY...POPS
WERE INCREASED INTO THE CHC CATEGORY NORTH OF THE MID HUDSON
VALLEY. IT IS POSSIBLE MOST OF THE DAYS COULD BE DRY DUE TO SOME
DRYING INDICATE IN THE COLUMN BASED ON THE SOUNDINGS. TEMPS LOOK
SEASONABLE...AND A SHADE ABOVE NORMAL FOR THE FIRST WEEKEND OF
MARCH.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
THE PATTERN DURING THE FIST PART OF THE PERIOD WILL FEATURE A
CONTINUATION OF A CYCLONIC FLOW REGIME CIRCULATING AROUND A CUT-OFF
UPPER LEVEL LOW OVER THE CANADIAN MARITIMES. THIS WILL RESULT IN A
NORTHERLY FLOW WITH A CHANCE OF SNOW SHOWERS IN THE MOUNTAINS...WITH
A SLIGHT CHANCE OF RAIN OR SNOW SHOWERS IN THE VALLEYS. PRECIP TYPE
IN VALLEY LOCATIONS WILL BE DIURNALLY DEPENDENT. OVERALL THIS
PATTERN SHOULD REMAIN OVER THE AREA THROUGH TUESDAY WITH
TEMPERATURES NEAR NORMAL.
THEN FOR THE MID WEEK PERIOD...ATTENTION WILL SHIFT TO A POSSIBLE
DEVELOPING STORM SYSTEM EMERGING OUT OF THE ROCKIES AND SOUTHERN
PLAINS...WHICH IS GENERALLY FORECAST TO TRACK ACROSS THE CAROLINAS
LATE TUESDAY INTO WEDNESDAY. AT THIS TIME MOST SOURCES OF MODEL
GUIDANCE DEPICT THIS SYSTEM TRACKING WELL SOUTH OF OUR AREA...BUT
THERE IS A DECENT AMOUNT OF SPREAD AS WELL. SO WHILE THE PROBABILITY
THIS STORM IMPACTS OUR AREA IS LOW...IT IS NOT ZERO AND WE WILL NEED
TO WATCH HOW THIS SYSTEM EVOLVES.
&&
.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
COMBINATION OF THE INFLUENCE FROM THE UPPER LOW NEARBY AND AN
OCCASIONAL WAVE PROVIDING A PERIOD OF LIGHT RAIN AND/OR SHOWER...WE
WILL KEEP AT LEAST MVFR CIGS IN THE TAFS AT THIS TIME. EXCEPTION
WOULD BE KPSF WHERE IFR CONDITION SHOULD PREVAIL THROUGH THE
REMAINDER OF THE OVERNIGHT PERIOD. PER THE ENHANCED IR
IMAGERY...SEEMS KPOU MIGHT CLEAR OUT TO ALLOW FOR QUICK VIS
REDUCTION TO IFR AND WE WILL PLACE THIS IN THE TAF.
DURING THE DAYLIGHT HOURS...WEST-NORTHWEST WINDS WILL INCREASE TO
LESS THAN 10 KTS WHICH SHOULD ASSIST WITH VISIBILITY IMPROVEMENTS
BUT THE CIGS SHOULD REMAIN INSIDE THE MVFR THRESHOLDS. MAIN
QUESTION WILL BE SHOWER COVERAGE AS WE WILL CONTINUE WITH THE VCSH
AT THIS TIME.
TONIGHT...LOW LEVEL MOISTURE REMAINS HIGH SO WE CAN ONCE AGAIN SEEN
CONDITIONS DROP INTO THE LOW MVFR OR INTO THE IFR CONDITIONS TOWARD
MIDNIGHT.
OUTLOOK...
FRI NT-MON...VFR/MVFR. SLIGHT CHC/CHC -SHSN/-SHRA.
TUE...VFR. NO SIG WX.
&&
.HYDROLOGY...
WIDESPREAD HYDRO PROBLEMS ARE NOT EXPECTED THE NEXT 5 DAYS. FLOWS
CONTINUE TO LOWER IN THE HOUSATONIC BASIN INCLUDING THE STILL
RIVER AT BROOKFIELD...WHERE IT CONTINUES TO FALL FROM THE ALERT
STAGE DUE TO THE RAIN AND SNOW MELT YESTERDAY.
ANY PRECIPITATION OVER THE NEXT FIVE DAYS WILL BE LIGHT WITH A
FEW HUNDREDTHS TO A COUPLE TENTHS OF AN INCH. THE MOUNTAINS WILL
HAVE MOSTLY SNOW. THE VALLEY LOCATIONS COULD HAVE LIGHT RAIN OR
SNOW WITH LITTLE OR NO ACCUMULATIONS.
OVERALL...MAIN STEM RIVERS SHOULD GENERALLY RECEDE INTO EARLY NEXT
WEEK.
FOR DETAILS ON SPECIFIC AREA RIVERS AND LAKES...INCLUDING OBSERVED
AND FORECAST RIVER STAGES AND LAKE ELEVATIONS...PLEASE VISIT THE
ADVANCED HYDROLOGIC PREDICTION SERVICE /AHPS/ GRAPHS ON OUR WEBSITE.
&&
.ALY WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
NY...NONE.
MA...NONE.
VT...NONE.
&&
$$
SYNOPSIS...FRUGIS/HWJIV
NEAR TERM...FRUGIS/HWJIV
SHORT TERM...WASULA
LONG TERM...JPV
AVIATION...BGM
HYDROLOGY...HWJIV/WASULA
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
330 AM CST FRI MAR 1 2013
.DISCUSSION...
330 AM CST
FORECAST CONCERNS ARE LAKE EFFECT SNOW SHOWER POTENTIAL THE NEXT FEW
DAYS...COLD TEMPERATURES OVER THE WEEKEND...AND A POSSIBLE SNOW
PRODUCING SYSTEM EARLY NEXT WEEK.
SHORT TERM...TODAY THROUGH SUNDAY NIGHT...
SLIGHTLY COLDER AIR MASS WILL SETTLE OVER THE REGION TODAY ON
CONTINUED NORTHERLY FLOW...WITH A LARGE AREA OF HIGH PRESSURE
BUILDING IN FROM THE NORTH. THIS SHOULD KEEP HIGHS A FEW DEGREES
COOLER THAN YESTERDAY. LAKE EFFECT SET UP IS QUITE MARGINAL
THERMODYNAMICALLY...BUT COMPENSATING SOMEWHAT WILL BE GOOD
CONVERGENCE AND FETCH WITH NORTH-NORTHEAST LOW LEVEL FLOW. THE
CONVERGENCE AND EVEN SOME ENHANCED LIFT IS BEST ALIGNED OVER
ILLINOIS AND PORTION OF NW INDIANA LAKEFRONT THROUGH MID/LATE
MORNING...SO BUMPED UP POPS SOME FROM PREVIOUS FORECAST. COULD SEE
SOME VERY LIGHT ACCUMULATIONS. OUTSIDE OF LAKE EFFECT...THERE MAY BE
SOME FLURRIES INLAND. ALTHOUGH STRATUS CAN CLEAR OUT QUICKER THIS
TIME OF YEAR DUE TO HIGHER SUN ANGLE...THINK THE NAM IS BEING WAY
TOO AGGRESSIVE WITH CLEARING TREND FROM NORTH. USED RAP GUIDANCE FOR
NEAR TERM SKY FORECAST. MOST OF CWA SHOULD SEE OVC THROUGH DAYLIGHT
HOURS.
THE SAME GENERAL IDEA OF DECENT CONVERGENCE BUT VERY MARGINAL
THERMODYNAMICS AND INVERSION HEIGHTS CONTINUES THROUGH SATURDAY WITH
THE LAKE EFFECT. WILL CONTINUE TO CARRY CHANCE POPS...THOUGH THEY
WILL SLIDE INTO NW INDIANA ON SATURDAY AS NORTHERLY FLOW BECOMES
JUST WEST OF DUE NORTH. SKIES SHOULD START TO CLEAR BY DAYBREAK OVER
THE NW CWA...SO TEMPERATURES SHOULD DROP PRETTY WELL THERE GIVEN
THE GOOD RADIATION COOLING...PROBABLY INTO THE MID TEENS.
OUTSIDE OF LAKE EFFECT CONCERNS...THE ONLY FOCUS OVER THE WEEKEND
WAS TEMPERATURES WITH HIGH PRESSURE BUILDING OVERHEAD. FOR HIGHS
ON SATURDAY...SUSPECT THAT THE MARCH SUN WILL GO TO WORK ON THE
SNOW COVER...ESPECIALLY FOR AREAS THAT DIDNT SEE MUCH THIS WEEK.
FOR MARCH 1-15...WITH 850 TEMPS AROUND -10C AS IS PROGGED ON
SATURDAY...MEDIAN HIGH AT ORD IS 34 DEGREES. WENT JUST UNDER THAT
IN NORTHERN CWA/ESPECIALLY IN THE NORTHEAST WHERE SNOW PACK IS
DEEPEST...YIELDING HIGHS AROUND 30. TO THE SOUTH OF I-80...SUSPECT
WE`LL SEE SOME MID TO EVEN UPPER 30S AS SUN EATS AWAY AT MEAGER
SNOW COVER.
THEN SUNDAY NIGHT...THERE IS A STRONG SIGNAL FOR GOOD RADIATIONAL
COOLING...ESPECIALLY ON THE ECMWF...WHICH MAY BE A BIT TOO
AGGRESSIVE WITH ITS ZERO TO SLIGHTLY BELOW ZERO NUMBERS FOR NORTH
CENTRAL IL. BASICALLY CONTINUED IDEA OF PREVIOUS FORECAST WITH
POTENTIAL FOR SINGLE DIGIT LOWS WEST OF FOX RIVER. ON SUNDAY...THE
COLD START MAY KEEP TEMPS IN CHECK SOMEWHAT...BUT MARCH SUN ANGLE
AND LONGER DAYLIGHT HOURS EXPECTED TO COMPENSATE...IN ADDITION TO
SLIGHTLY WARMER TEMPS ALOFT. MEDIAN ORD HIGHS FOR DAYS WITH 850
TEMPS AS PROGGED ON SUNDAY IN -6 TO -8 RANGE IS 38. DIDNT GO THIS
MILD DUE TO COLD START AND SNOW COVER OVER NORTHERN CWA...BUT
BUMPED UP TEMPS A FEW DEGREES FROM PREVIOUS. IF SNOW COVER CAN BE
ELIMINATED ON SATURDAY OVER SOUTH...WOULDNT BE SURPRISED IF SOME
LOCATIONS TAG 40 DEGREES...BUT FOR NOW WENT WITH UPPER 30S IN
CENTRAL IL. INCREASING CLOUD COVER SHOULD RESULT IN LOWS SEVERAL
DEGREES WARMER SUNDAY NIGHT THAN SATURDAY NIGHT.
LONG TERM...MONDAY THROUGH THURSDAY
MAIN FOCUS IS ON VERY ENERGETIC CLIPPER SYSTEM EARLY NEXT WEEK.
THERE HAVE BEEN FAIRLY SIGNIFICANT RUN TO RUN CHANGES WITH THE
TIMING AND TRACK OF THE STRONG UPPER LOW AND SURFACE REFLECTION.
WOULD EXPECT THIS TO CONTINUE UNTIL UPPER WAVE MAKES LANDFALL IN
PACIFIC NORTHWEST SATURDAY NIGHT ALLOWING FOR SAMPLING BY RAOB
NETWORK. AS IT STANDS RIGHT NOW...00Z GUIDANCE HAS SHIFTED BACK
NORTH...WHICH WOULD PUT MOST OF CWA IN LINE FOR A POTENTIALLY
ACCUMULATING SNOW. COULD SEE THE START OF SOME WAA SNOWS AHEAD OF
SYSTEM ON MONDAY...SO BLENDED POPS WERE MAINTAINED.
HOWEVER...BIGGEST CHANGE WAS TO GREATLY INCREASE POPS ABOVE
ALLBLEND MONDAY NIGHT AND TUESDAY IN LINE WITH A SLOWER
PROGRESSION OF THE UPPER LOW AND ATTENDANT SURFACE LOW FAVORED BY
THE 00Z ECMWF...CANADIAN...GEFS AND HPC. GFS APPEARS MUCH TOO FAST
IN CLEARING THE SYSTEM OFF TO THE EAST. FOR NOW...BUMPED UP POPS
TO MID RANGE CHANCE GIVEN UNCERTAINTY.
AS CURRENTLY MODELED...THE UPPER LOW WITH THIS SYSTEM LOOKS QUITE
STRONG...WITH A TIGHT BAROCLINIC ZONE ALONG/AHEAD OF ITS TRACK. THUS
THERE COULD BE A NICE SWATH OF SNOW PUT DOWN SOMEWHERE OVER/NEAR THE
REGION. ON THE NEGATIVE SIDE...TEMPERATURES AS IS USUALLY THE CASE
IN MARCH WOULD BE NEAR FREEZING...SO THE SNOW WOULD HAVE TO COME
DOWN HARD TO ACCUMULATE EFFICIENTLY. LOTS OF TIME TO MONITOR THIS
SYSTEM.
FOR THE REST OF THE EXTENDED AND BEYOND...AFTER A FAIRLY COOL DAY ON
WEDNESDAY BEHIND THE EARLY WEEK SYSTEM...THERE COULD BE BRIEF WARM UP
TO NORMAL TO ABOVE NORMAL AS THE PATTERN TRANSITIONS FROM AN EASTERN
TROUGH/WESTERN RIDGE (POSITIVE PNA) CONFIGURATION TO A WESTERN
TROUGH/EASTERN RIDGE (NEGATIVE PNA) PATTERN. WITH RIDGING FIRST
AMPLIFYING INTO CENTER OF CONUS...WE COULD SEE A FEW DAYS OF
TEMPERATURES AT LEAST BACK INTO THE 40S.
HOWEVER...THE LONG RANGE ENSEMBLES LOOKING BEYOND THIS 7 DAY
FORECAST PERIOD ARE HOLDING ONTO THE IDEA OF MAINTAINING HIGH
LATITUDE BLOCKING/NEGATIVE NAO AND NEGATIVE AO THROUGH MID MARCH.
IN ADDITION...RIDGING MAY AMPLIFY OVER OR NEAR ALASKA WHICH ALLOWS
FRESH COLD AIR TO INFILTRATE CANADA AND THE NORTHERN CONUS. BOTTOM
LINE IS ANY WARM UP COULD BE QUICKLY FOLLOWED BY A RETURN TO THE
COLDER THAN NORMAL PATTERN. NO MARCH 2012 PATTERN IS SEEN IN THE
EXTENDED FOR ANYONE HOPING FOR AN EARLY SUMMER AGAIN.
RC
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 09Z...
* OCCASIONAL FLURRIES AND POSSIBLY SCT -SHSN...ESPECIALLY THRU
EARLY FRI AFTERNOON
* NNW WINDS TO TRANSITION TO NE FRIDAY MORNING
IZZI
//DISCUSSION...UPDATED 06Z...
EXTENSIVE HIGH END MVFR/LOW END VFR STRATUS DECK BLANKETS THE
REGION WITH SOME POCKETS OF FLURRIES/VERY LIGHT SNOW SHOWERS
LIKELY TO TO PERSIST THRU THE TAF CYCLE. LAKE EFFECT SNOW SHOWERS
WILL HAVE A TENDENCY TO BACK WEST INTO NE IL FRIDAY MORNING AND
COULD BRING SOME TEMPO VSBY RESTRICTIONS TO MVFR AND POSSIBLY
BRIEFLY IFR IN -SN TO ORD/MDW FRI MORNING/EARLY AFTERNOON. LAND
BREEZE INFLUENCE TO WIND DIRECTION SHOULD RESULT IN WEST OF DUE
NORTH WINDS INTO EARLY FRIDAY MORNING AT CHGO AREA TERMINALS WITH
TRANSITION TO MORE NE WINDS EXPECTED AT SOME POINT FRIDAY MORNING.
IZZI
//ORD AND MDW CONFIDENCE...UPDATED 09Z...
* LOW/MEDIUM CONFIDENCE IN -SHSN POTENTIAL
* HIGH CONFIDENCE IN WIND SHIFT TO NE...BUT LOW CONFIDENCE IN
TIMING
* MEDIUM/HIGH CONFIDENCE IN CIGS FORECAST THROUGH THE PERIOD
IZZI
//OUTLOOK FOR ORD/MDW FOR 12Z SATURDAY-12Z THURSDAY...UPDATED 00Z...
SATURDAY AND SUNDAY...VFR.
MONDAY AND TUESDAY...CHANCE FOR SNOW AND MVFR.
WEDNESDAY...VFR.
MDB
&&
.MARINE...
222 AM CST
MODERATELY STRONG NORTH WINDS LIKELY TO CONTINUE THROUGH SATURDAY
WITH OCCASIONAL GALE FORCE GUSTS A POSSIBILITY...ESPECIALLY LATER
THIS AFTERNOON INTO THE EVENING...BUT GENERALLY THINK ANY GALES
WILL BE INFREQUENT ENOUGH TO KEEP OUT OF THE FORECAST. WINDS WILL
BEGIN TO DIMINISHING LATER SATURDAY INTO SUNDAY AS RIDGE AXIS
APPROACHES AND THEN MOVES ACROSS THE LAKE SUNDAY NIGHT. ANOTHER
SYSTEM WILL PASS TO THE SOUTHWEST OF THE LAKE EARLY/MIDDLE PART OF
NEXT WEEK WITH WINDS FRESHENING UP A BIT...BUT SYSTEM SHOULD BE
WEAK ENOUGH AND FAR ENOUGH AWAY TO NOT CAUSE ANY MAJOR
WINDS/WAVES.
IZZI
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
UNTIL 10 PM SATURDAY.
&&
$$
AREA FORECAST DISCUSSION
NWS NORTHERN INDIANA
444 AM EST FRI MAR 1 2013
.SHORT TERM...TODAY THROUGH SATURDAY NIGHT
RELATIVELY QUIET PERIOD IN STORE FOR THE UPCOMING WEEKEND WITH MAIN
SHORT TERM FOCUS ON LINGERING LIGHT PRECIP THIS MORNING...AND
TEMPERATURE TRENDS.
WATER VAPOR IMAGERY/07Z RAP ANALYSIS SUGGEST WEAK UPPER VORT MAX
DROPPING SOUTHWARD ACROSS NORTHERN INDIANA THIS MORNING. HAVE NOTED
SOME UPSWING OVER PAST HOUR ACROSS CENTRAL/SOUTHERN SECTIONS OF
FORECAST AREA OF SOME -FZDZ PER RADAR/SFC OBSERVATIONS BUT FZDZ IS
EXPECTED TO REMAIN LIGHT ENOUGH TO PREVENT SIGNIFICANT IMPACTS THIS
MORNING. WITH AXIS OF WEAK DPVA SHIFTING ACROSS SOUTHERN/CENTRAL
AREAS WILL CONFINE EARLY MORNING FZDZ MENTION TO THESE LOCATIONS
WITH MAINLY DRY CONDITIONS ACROSS THE NORTH WERE LOW LEVEL DRY AIR
ADVECTION HAS BECOME MORE PRONOUNCED IN THE WAKE OF ASSOCIATED WEAK
INVERTED SFC TROUGH FEATURE. MARINE OBS SUGGEST SOME AUGMENTATION TO
SYNOPTIC CONVERGENCE ASSOCIATED WITH THIS TROUGH WITH WEAK LAKE
INDUCED THERMAL TROUGHING. THIS MAY ACT TO PERPETUATE SOME FLURRIES
ACROSS EXTREME NORTHWEST SECTIONS OF THE FORECAST AREA
TODAY...ALTHOUGH INCREASINGLY DRY LOW LEVEL AIR MASS SHOULD LIMIT
FLURRY/LIGHT SNOW SHOWER ACTIVITY. LIMITED DIURNAL MOVEMENT IN
TEMPERATURES EXPECTED AGAIN TODAY WITH RELATIVELY WEAK THERMAL
ADVECTION AND PERSISTENCE OF LOW CLOUD DECK.
FOR TONIGHT INTO SATURDAY...LONGWAVE RIDING ACROSS WESTERN CONUS
WILL BEGIN TO SHIFT EASTWARD AS WEAK UPPER PV ANOMALY ACROSS
NORTHERN PLAINS ADVANCES INTO THE WESTERN GREAT LAKES REGION. UPPER
FORCING/DYNAMICS LOOK TO BE QUITE WEAK WITH THIS SHORT WAVE HOWEVER
AS PV ANOMALY BECOMES AFFECTED BY MID/UPPER LEVEL DEFORMATION FLOW
ACROSS GREAT LAKES REGION. PASSAGE OF THIS FEATURE MAY MARK A SUBTLE
UPSWING IN WEAK LAKE RESPONSE IN THE FORM OF SCT FLURRIES/LIGHT SNOW
SHOWERS SATURDAY/SATURDAY NIGHT. LAKE EFFECT PARAMETERS QUITE MEAGER
HOWEVER WITH VERY DRY MID LEVEL AIR IN PLACE...AND MARGINAL LAKE/850
HPA DELTA TEMPS. DESPITE SOME WEAK REINFORCING LOW LEVEL CAA WITH
AFOREMENTIONED NORTHERN PLAINS SHORT WAVE SATURDAY...HIGH TEMPS
SHOULD BE SIMILAR TO THAT OF FRIDAY WITH THE POSSIBILITY OF A BIT
MORE INSOLATION OFFSETTING SLIGHTLY COOLER LOW LEVEL THERMAL
PROFILES.
&&
.LONG TERM...
SUNDAY THROUGH THURSDAY...THE MAIN CHALLENGE THIS PERIOD IS THE
TIMING AND TRACK OF A SHORT WAVE THAT WILL TOP THE UPSTREAM RIDGE
AND MOVE INTO THE MIDWEST NEXT WEEK. THE ECMWF APPEARS TO HAVE
INITIALIZED THIS SYSTEM REASONABLY WELL AND HAS ALSO SHOWN SOME RUN
TO RUN CONSISTENCY. FOR THIS PACKAGE...BLENDED SEVERAL MODELS
INCLUDING THE ECMWF OPERATIONAL RUN...EC ENSEMBLE MEAN...AND GFS
OPERATIONAL RUN WITH ENSEMBLE MEMBERS. GIVEN THE HIGH LATITUDE
STRONG POSITIVE ANOMALY...CONCERN THAT THESE MODELS MAY BE TOO FAST
WITH THIS SYSTEM. THE ECMWF HAS TRENDED SLIGHTLY SLOWER WITH THIS
SYSTEM WITH AN ARRIVAL TIME OF TUESDAY/TUESDAY NIGHT. HAVE TRENDED
THE SNOW CHANCES HIGHER THESE PERIODS...BUT KEPT IN CHANCE CATEGORY
DUE TO A LARGE GFS ENSEMBLE SPREAD AND LARGE NORMALIZED STANDARD
DEVIATIONS AMONG ECMWF ENSEMBLE MEMBERS. A WEAK LAKE RESPONSE IS
EXPECTED AFTER THIS SYSTEM PASSES...BUT DELTA T VALUES SHOULD REMAIN
LESS THAN 10. OTHERWISE...KEPT TEMPERATURES COLD THROUGH WEDNESDAY.
TEMPS SHOULD RISE ABOVE NORMAL THURSDAY AS AN UPPER LEVEL RIDGE
BUILDS OVER THE REGION. GFS MEAN ENSEMBLE MEX MOS TEMPS APPEAR ON
TRACK.
&&
.AVIATION...
06Z TAFS...A WEAK UPPER LEVEL SHORT WAVE ACROSS CENTRAL LOWER
MICHIGAN WILL CONTINUE TO GET SHEARED AS IT REACHES NORTHERN
INDIANA OVERNIGHT. THIS WEAKENING FORCING COMBINED WITH THE ONSET
OF DRY AIR ADVECTION SHOULD RESULT IN REDUCED INTENSITY OF DZ/FZDZ
OVERNIGHT. A FEW FLURRIES STILL POSSIBLE IN VICINITY OF UPPER VORT
MAX...BUT NOT EXPECTING SIGNIFICANT VSBY RESTRICTIONS. TRAPPED LOW
LEVEL MOISTURE SHOULD RESULT IN CONTINUED MVFR CIGS
OVERNIGHT...WITH IMPROVEMENT TO HIGHER END MVFR EXPECTED BY LATE
MORNING. DIURNAL TENDENCIES SHOULD RESULT IN TREND TO VFR LOW
CLOUDS BY MID AFTERNOON.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 5 AM EST SUNDAY FOR LMZ043-046.
&&
$$
SHORT TERM...MARSILI
LONG TERM...SKIPPER
AVIATION...MARSILI
AREA FORECAST DISCUSSION
NWS BISMARCK ND
326 AM CST FRI MAR 1 2013
.SHORT TERM...TODAY THROUGH SATURDAY...
THE MAIN CHALLENGE FOR THE SHORT TERM IS THE EVOLUTION OF THE
STRATUS ACROSS NORTHWEST AND CENTRAL NORTH DAKOTA TODAY...WITH
MILD TEMPERATURES HIGHLIGHTING THE SOUTHWEST AND SOUTH CENTRAL ON
SATURDAY.
AS HAS BEEN THE CASE IN MOST STRATUS EVENTS THIS WINTER...THE RAP
AND HRRR HAVE THE BEST HANDLE ON THE ONGOING STRATUS ACROSS
NORTHWEST AND CENTRAL NORTH DAKOTA THIS MORNING. GIVEN LITTLE
MIXING...WILL FOLLOW CLOSELY TO THE LATEST RAP RUNS WHICH SLOWLY
ERODE THE STRATUS...YET MAINTAIN ITS PRESENCE ACROSS CENTRAL
NORTH DAKOTA THROUGH MUCH OF THE DAY. MAINTAINED THE MENTION OF
ISOLATED FLURRIES UNDER THE STRATUS THROUGH THE MORNING...WITH
PATCHY FOG ALSO POSSIBLE THIS MORNING FOR ALL AREAS WITH STRATUS
BUILD DOWN OR VIA RADIATIONAL EFFECTS ACROSS THE CLOUD FREE
SOUTHWEST. IN REGARDS TO TEMPERATURES FOR TODAY...PREFERRED THE
BIAS CORRECTED 00 UTC ECMWF/GEM AND BIAS CORRECTED RAP WHICH HAVE
SHOWN SUPERIOR SHORT TERM TEMPERATURE VERIFICATION AND CAPTURE THE
IMPACTS OF BARE GROUND...WITH HIGHS IN THE UPPER 40S FAR
SOUTHWEST. UNDER THE STRATUS OVER THE DEEPER SNOW PACKS OF THE
NORTH CENTRAL AND JAMES RIVER VALLEY...HIGHS WILL GENERALLY RANGE
IN THE LOWER TO MID 20S.
FOR TONIGHT...A RATHER MILD OVERNIGHT IS EXPECTED SOUTHWEST WITH
LOWS ONLY DROPPING INTO THE LOWER 30S WITH THE ONSET OF RETURN FLOW.
AGAIN...THE IMPACTS OF THE SNOWPACK WILL BE NOTED FROM THE TURTLE
MOUNTAINS THROUGH THE JAMES RIVER VALLEY WITH LOWS NEAR 10 WITH A
LATER COMMENCEMENT OF RETURN FLOW TONIGHT. GIVEN THE POSSIBILITY
OF NON-DIURNAL TEMPERATURE TRENDS FOR TONIGHT...FOLLOWED THE
CONSENSUS OF THE 00 UTC DETERMINISTIC MODELS WHICH SHOULD CAPTURE
THIS PATTERN.
ONCE AGAIN...THE SUPERIOR PERFORMING BIAS CORRECTED 00 UTC
ECMWF/GEM WERE FAVORED FOR TEMPERATURES ON SATURDAY...WITH HIGHS
IN THE UPPER 50S POSSIBLE FOR THE BARE GROUND OF THE FAR SOUTHWEST
WITH GOOD MIXING AND SUNSHINE IN THE WAKE OF A SURFACE WARM FRONT
THAT WILL APPROACH THE HIGHWAY 83 CORRIDOR BY 18 UTC. WITH STRATUS
EXPECTED TO BE TRAPPED UNDER THE WARM FRONTAL INVERSION ACROSS
CENTRAL NORTH DAKOTA THROUGH MUCH OF THE DAY...HIGHS WILL ONLY
RECOVER TO THE UPPER 20S FROM THE TURTLE MOUNTAINS THROUGH THE
JAMES RIVER VALLEY. FOR THE SOUTH CENTRAL...HIGHS IN THE LOWER TO
UPPER 40S ARE EXPECTED AND ARE DEPENDENT ON HOW MUCH SUNSHINE IS
RECEIVED.
.LONG TERM...SATURDAY NIGHT THROUGH THURSDAY...
THE MAIN FEATURE IN THE LONG TERM PERIOD WILL BE A STORM SYSTEM
MOVING ACROSS THE NORTHERN ROCKIES AND INTO THE PLAINS SUNDAY
THROUGH MONDAY NIGHT.
LOOKING AT THE DETERMINISTIC MODELS...THERE HAS BEEN A COMPLETE FLIP
FLOP BETWEEN THE GFS/ECMWF. THE GFS IS NOW THE OUTLIER WITH A
FARTHER SOUTH TRACK WITH THE SYSTEM WITH MORE DRY AIR TO THE NORTH.
THIS LIMITS PRECIPITATION TO THE WEST AND SOUTH CENTRAL. THE ECMWF
IS MORE IN LINE WITH THE GEM...SPREADING PRECIPITATION ACROSS ALL OF
WESTERN AND CENTRAL NORTH DAKOTA...WITH A QPF MAXIMA OVER NORTH
CENTRAL INTO EASTERN NORTH DAKOTA. THE GEM IS THE MOST CONSISTENT OF
THE THREE SPREADING A GOOD AMOUNT OF PRECIPITATION ACROSS ALL OF
WESTERN AND CENTRAL NORTH DAKOTA.
AS WE BEGIN THE LONG TERM PERIOD SATURDAY NIGHT...THE UPPER LEVEL
TROUGH IS JUST MOVING ONTO THE NORTHWEST U.S. SOUTHERN BRITISH
COLUMBIA COAST...WITH UPPER LEVEL RIDGING FROM THE NORTHERN ROCKIES
INTO THE NORTHERN PLAINS. DURING THE NIGHT THE UPPER LOW MOVES ON
SHORE AND INTO THE NORTHERN ROCKIES...RESULTING IN SURFACE LOW
PRESSURE DEVELOPING IN THE LEE OF THE NORTHERN ROCKIES. THIS SHOULD
ALLOW FOR A MILD OVERNIGHT WITH AN INCREASING SOUTHEAST SURFACE FLOW
AND AN INFLUX OF MOISTURE INTO THE NORTHERN PLAINS. OVERNIGHT LOWS
MAY REMAIN ABOVE FREEZING ACROSS THE SOUTHWEST...TRANSITIONING TO
THE TEENS OVER THE NORTHEAST CWA.
THE ECMWF IS THE MOST AGGRESSIVE IN SPREADING PRECIPITATION INTO THE
LOCAL AREA ON SUNDAY...BUT BY SUNDAY AFTERNOON ALL DETERMINISTIC
MODELS BRING PRECIPITATION INTO WESTERN AND CENTRAL NORTH DAKOTA.
THE MAIN DIFFERENCE IS THE THERMAL PROFILES WITH THE ECMWF BEING
MUCH WARMER AND KEEPING PRECIPITATION MAINLY RAIN EXCEPT FOR THE
NORTHERN TIER COUNTIES. WITH A COLDER EAST TO NORTHEAST FLOW THE GFS
DEPICTS TEMPERATURES CONDUCIVE TO SNOW FOR ALL BUT THE FAR
SOUTHWEST. BUT WITH THE DRIER EAST FLOW...IS NOT AS AGGRESSIVE IN
SPREADING PRECIPITATION INTO EASTERN PORTIONS OF THE CWA. THESE
DIFFERENCES WILL BE A BIG FACTOR IN RESULTING HIGH TEMPERATURES ON
SUNDAY AND CONSIDERING THE DIFFERENCES...WILL STICK WITH A MODEL
BLEND.
SUNDAY NIGHT AND MONDAY WILL BE THE KEY PERIODS FOR SNOWFALL
POTENTIAL. IT APPEARS AT THIS TIME...AT LEAST A PORTION OF THE CWA
WILL RECEIVE SIGNIFICANT SNOWFALL DUE TO THE DYNAMICS OF THE UPPER
LEVEL SYSTEM AND THE RESULTING FRONTOGENETIC FORCING WITH A STRONG
THERMAL PROFILE SETTING UP. THE MAIN QUESTION IS WILL IT BE FROM THE
NORTH CENTRAL INTO EASTERN NORTH DAKOTA PER THE ECMWF...THE
SOUTHWEST QUARTER PER THE GFS...OR A BROAD SOLUTION COVERING THE
ENTIRE CWA.
TWO MAIN FACTORS ARE IN PLAY HERE FOR POSSIBLE HIGHLIGHTS. FIRST THE
MODEL DIFFERENCES AND SECOND THE TIMING OF THE EVENT. WITH THE
INCONSISTENCIES BETWEEN THE GFS/ECMWF...FEEL A LITTLE MORE TIME
WOULD BE A GOOD DECISION BEFORE THE ISSUANCE OF ANY HIGHLIGHTS. IT
LOOKS LIKE THE STRONGEST FORCING AND THIS GREATEST SNOW POTENTIAL
WILL NOT BEGIN UNTIL SUNDAY NIGHT. THIS WOULD EVEN BE ON THE FAR END
FOR A WATCH IF ISSUED THIS MORNING. THEREFORE WILL HOLD OFF ON ANY
HIGHLIGHTS AT THIS TIME.
PRECIPITATION ENDS MONDAY NIGHT AND MAINLY DRY CONDITIONS ARE
EXPECTED TUESDAY AND WEDNESDAY. THERE ARE ALSO BIG DIFFERENCES
BETWEEN THE GFS/ECMWF WITH THE NEXT SYSTEM ON THURSDAY. WILL UTILIZE
A BLEND HERE.
&&
.AVIATION...
LOW PRESSURE OVER MONTANA AND HIGH PRESSURE OVER
ONTARIO IS PRODUCING AN AREA OF LOW LEVEL CONVERGENCE ACROSS WESTERN
AND CENTRAL NORTH DAKOTA WITH IFR CEILINGS AT KBIS AND KMOT AND MVFR
CEILINGS AT KISN. MAINLY CLEAR SKIES AT KDIK AND KJMS. WITH A WEAK
SURFACE FLOW...EXPECT MVFR-IFR CONDITIONS TO PERSIST THROUGH THE
MORNING ISN...KDIK...KMOT AND KBIS. WITH MOISTURE DISSIPATING BY
THIS AFTERNOON AS SOUTHERLY FLOW INCREASES. THEN MAINLY VFR
CONDITIONS EXPECTED TONIGHT.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...AYD
LONG TERM/AVIATION...AYD
AREA FORECAST DISCUSSION
NWS BISMARCK ND
109 AM CST FRI MAR 1 2013
.DISCUSSION...
NO SIGNIFICANT CHANGES WERE REQUIRED WITH THIS FORECAST UPDATE AS
THE INHERITED FORECAST FOR THE REMAINDER OF THE NIGHT IS WELL ON
TRACK...AND WAS BLENDED TO THE 07 UTC OBSERVED TRENDS.
AS HAS BEEN THE CASE...THE LATEST RUNS OF THE RAP AND HRRR HAVE A
GOOD HANDLE ON THE STRATUS FIELD ACROSS MUCH OF NORTHWEST AND
CENTRAL NORTH DAKOTA. GIVEN THE LACK OF MIXING...FOLLOWED CLOSELY
TO THE LATEST RAP RUNS FOR CLOUD COVER TONIGHT THROUGH THE DAY ON
FRIDAY...WHICH HOLDS THE STRATUS ACROSS THE CENTRAL INTO THE
AFTERNOON. DO EXPECT THE CURRENT STRATUS FIELD TO CONTINUE TO
BUILD DOWN THROUGH THE NIGHT TONIGHT...WITH PATCHY FOG POSSIBLE
FOR MOST AREAS. THE MOST WIDESPREAD AND DENSE FOG IS LIKELY TO BE
ACROSS THE NORTHWEST WITH A WEAK UPSLOPE FLOW COMPONENT.
&&
.AVIATION...
HE MAIN IMPACTS TO AVIATION IS THE THREAT OF MVFR/IFR CIGS AND
VSBYS IN FOG FOR THE 06Z TAF ISSUANCE. CURRENTLY THERE IS A WEAK
SURFACE TROUGH OVER THE WESTERN DAKOTAS THAT EXTENDS NORTHWESTWARD
INTO SOUTHWESTERN SASKATCHEWAN AND NORTHERN ALBERTA. THIS TROUGH
DEFINES THE WESTERN EDGE OF A LARGE HIGH PRESSURE SYSTEM...WITH A
SWATH OF IFR/MVFR/VFR CLOUDS EXTENDING ALONG THIS BOUNDARY FROM
NORTHERN SASKATCHEWAN THROUGH CENTRAL ND TO EASTERN SD. THE MODELS
INDICATE THIS SURFACE TROUGH REMAINING NEARLY STATIONARY OVERNIGHT.
EXPECTING MVFR/IFR CIGS AT KISN/KMOT/KBIS WITH SOME MVFR VSBYS IN
LIGHT FOG. EXPECT MVFR/IFR CIGS TO EVENTUALLY EXPAND EASTWARD INTO
KJMS...AND EXPAND SOUTHWARD/SOUTHWESTWARD INTO KDIK. TIMING OF FOG
FORMATION IS PROBLEMATIC BUT HAVE DECREASED VSBYS GRADUALLY AFT
AROUND 08Z/09Z.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...AYD
AVIATION...JV
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
308 AM CST FRI MAR 1 2013
.SHORT TERM...TODAY THROUGH SUNDAY NIGHT
308 AM CST FRI MAR 1 2013
POTENTIAL FOR ACCUMULATING SNOW SUNDAY NIGHT AND HEADING INTO THE
LONG TERM PERIOD.
CURRENTLY AS OF 09Z...WATER VAPOR LOOP AND RAP 500MB HEIGHT ANALYSIS
SHOWED RIDGING OVER THE WESTERN U.S. INTO ALBERTA AND GENERAL BROAD
TROUGHING OVER THE EAST HALF OF THE U.S.. THE FORECAST AREA SITS IN
A NON-DESCRIPT FLOW WITHIN THIS BROAD TROUGH...DUE TO THE MAIN JET
FLOW CONFINED OVER THE WESTERN DAKOTAS...AND AN UPPER LOW STUCK OVER
NEW ENGLAND. THIS NON-DESCRIPT FLOW HAS RESULTED IN THE VERY SLOW
SURFACE PATTERN PROGRESSION...WITH THE AREA STILL UNDER CYCLONIC
FLOW AROUND LOW PRESSURE IN NEW ENGLAND. A TROUGH EXTENDING WEST
FROM THE LOW EXTENDS WEST NEAR I-80 TO DES MOINES...THEN TO THE
NORTHWEST TO FARGO. SLOWLY DRIER AIR IS ADVECTING SOUTHWARD INTO THE
CYCLONIC CIRCULATION FROM HIGH PRESSURE OVER HUDSON BAY...RESULTING
IN CLEARING OVER NORTHERN LAKE SUPERIOR INTO THE NORTHERN 2/3 OF
MINNESOTA. HOWEVER...THE 00Z MPX AND GRB SOUNDINGS STILL SHOW A 50MB
SATURATED LAYER STUCK AROUND A COLD FRONTAL INVERSION SITTING AT
825MB. THUS...STRATUS STILL COVERS THE AREA. THIS STRATUS COMBINED
WITH A 5-10 KT NORTHEAST WIND HAS KEPT TEMPERATURES MAINLY IN THE
20S...DESPITE 850MB TEMPS AROUND -11C OR 1 STANDARD DEVIATION BELOW
NORMAL PER 00Z RAOBS.
SHORT TERM HIGHLIGHTS / CONCERNS:
1. WHEN WILL IT CLEAR
THIS IS A TWO PART ISSUE. FIRST AND MORE IMPORTANTLY IS THE GENERAL
STRATUS DECK IN PLACE. 01.00Z NAM WAS SURPRISINGLY TOO AGGRESSIVE
WITH CLEARING...SUGGESTING BASED ON 850MB AND 900MB RH FIELDS THAT
LOCATIONS NORTH OF I-90 WOULD BE CLEAR RIGHT NOW. LATEST RAP 850MB
AND 900MB RH GUIDANCE SEEMS TO HAVE A BETTER HANDLE ON THE LOW
CLOUDS...GRADUALLY CLEARING LOCATIONS NORTH OF I-90 NORTH TO SOUTH
THROUGH 21Z. A COMBINATION OF DAYTIME MIXING AND A STRONGER SURGE OF
DRY AIR FROM NORTHERN ONTARIO APPEARS TO BE AIDING IN THIS CLEARING.
SOUTH OF I-90...THE LOW CLOUDS MAY NOT DISSIPATE UNTIL SOMETIME
DURING THE EVENING. THE SECOND PART OF THE CLEARING ISSUE IS IN THE
UPPER LEVELS WHERE SCT-BKN CIRROSTRATUS EXISTS OVER THE AREA. THE
NON-DESCRIPT UPPER LEVEL FLOW WOULD SUGGEST CLEARING OF THE CIRRUS
WILL BE PROBLEMATIC. NAM/RAP 500-400MB RH FIELD CONFIRM THIS AS WELL
WITH MUCH OF THE AREA DOMINATED BY SCT-BKN CIRROSTRATUS THROUGH THE
DAY TODAY...ESPECIALLY OVER THE WESTERN HALF. IT LOOKS LIKE WE
FINALLY CAN CLEAR THESE HIGH CLOUDS OUT TONIGHT INTO SATURDAY
MORNING AS THE UPPER RIDGE OVER THE WESTERN U.S. BEGINS PROGRESSING
EAST.
2. TEMPERATURES TODAY THROUGH SATURDAY NIGHT
THE STRONGER NOW EARLY MARCH SUN CAN DEFINITELY WARM TEMPERATURES
UP...EVEN UNDER AN ENVIRONMENT OF COLD 850MB TEMPS...LIKE THOSE
TODAY AROUND -11C. HOWEVER...WITH ONLY PARTIAL CLEARING OVERALL
NORTH OF I-90...IT LOOKS TOUGH TO GET TEMPERATURES TO OR ABOVE
FREEZING. NAM 2 METER AND MET GUIDANCE LOOKS A BIT TOO OPTIMISTIC...
GIVEN THE FACT THAT IT HAS CLEARING MUCH EARLIER THAN WHAT WILL
OCCUR. HAVE LEANED MORE TOWARDS MAV/ECMWF/GEM GUIDANCE AS A RESULT.
RELATIVELY COOL CONDITIONS TODAY COMBINED WITH CLEARING TONIGHT AND
WINDS CALMING WITH HIGH PRESSURE BUILDING IN SETS THE STAGE FOR A
DECENT RADIATIONAL COOLING NIGHT. THUS...STAYED TOWARD THE COOL END
OF GUIDANCE. MUCH MORE SUN ON SATURDAY WITH SIMILAR 850MB TEMPS WILL
YIELD JUST A SLIGHTLY WARMER DAY. THE SURFACE HIGH PRESSURE RIDGE IS
PROGGED TO REMAIN NEARBY SATURDAY NIGHT...WHICH AGAIN PUTS A GOOD
RADIATIONAL COOLING NIGHT IN FOCUS. HOWEVER...MID AND HIGH CLOUDS
LOOK TO INCREASE COMING THROUGH THE UPPER RIDGE BUILDING TOWARDS US.
THUS...WE SHOULD NOT GET AS COOL AS TONIGHT. STILL...TIMING OF THE
CLOUDS IS EVERYTHING AND TYPICAL COLD SPOTS IN WISCONSIN COULD STILL
END UP PLUMMETING. THUS...FOR THE TYPICAL COLD SPOTS LEANED MORE
TOWARDS THE COLDER SIDE OF GUIDANCE FOR THEM.
3. POTENTIAL FOR WARM ADVECTION PRECIPITATION SUNDAY/SUNDAY NIGHT
MODELS ARE PROGGING THAT A POTENT UPPER TROUGH...CURRENTLY PRESENT
NEAR 45 N / 150W WELL SOUTH OF THE GULF OF ALASKA...WILL CRASH
THROUGH THE UPPER RIDGING BUILDING TOWARDS THE FORECAST AREA DURING
THE WEEKEND. BY 12Z SUNDAY...GOOD MODEL AGREEMENT EXISTS THAT THIS
POTENT UPPER TROUGH...PERHAPS IN THE FORM OF A CLOSED LOW...SHOULD
BE OVER WASHINGTON STATE. THERE STILL REMAINS SOME DISAGREEMENT ON
THE TRACK OF THE POTENT UPPER TROUGH AFTERWARDS...BUT THERE DOES
APPEAR TO BE A CONVERGING SOLUTION. BY 12Z MONDAY...THE TROUGH
SHOULD EXIST SOMEWHERE BETWEEN ENTERING WESTERN SOUTH DAKOTA
/SLOWER 01.00Z ECMWF/ TO SOUTHEAST SOUTH DAKOTA /FASTER 01.00Z NAM/.
THE SPEED FACTOR APPEARS TO BE RELATED TO HOW POTENT A SHORTWAVE IS
DROPPING THROUGH MICHIGAN ON SUNDAY...THE MORE POTENT THE SLOWER THE
UPPER TROUGH COMING ACROSS THE NORTHERN ROCKIES WILL BE. THIS
FORECAST IS GOING TO TAKE A CONSENSUS APPROACH TO THE 01.00Z
GUIDANCE...GIVEN THE CONVERGING TREND BUT AT THE SAME TIME ALLOWS
FOR A LITTLE CONTINUITY.
DETAILS...AS THE POTENT TROUGH DIGS INTO THE NORTHERN ROCKIES ON
SUNDAY...LOW PRESSURE DEEPENS DOWNSTREAM OVER SOUTH DAKOTA AND
NEBRASKA. IN TURN...WARM ADVECTION INTENSIFIES...DEVELOPING A MASS
OF MID CLOUDS FROM THE DAKOTAS INTO THE FORECAST AREA. THE 00Z
GFS/UKMET/CANADIAN ALL DEVELOP SOME LIGHT PRECIP WEST OF THE
MISSISSIPPI RIVER BETWEEN 18-00Z...BUT UNSURE IF THIS IS GOING TO
REACH THE GROUND AS REFLECTED BY THE 00Z ECMWF. INCLUDED JUST A 20
PERCENT CHANCE OVER SOUTHEAST MN FOR NOW. CHANCES INCREASE
EVERYWHERE SUNDAY NIGHT...ESPECIALLY WEST OF THE MISSISSIPPI
RIVER...ASSOCIATED WITH THE TROUGH PUSHING EAST AND MORE IMPORTANTLY
THE LOW TO MID-LEVEL FRONTOGENESIS ZONE STRENGTHENING. INCREASED
CHANCES TOWARD 60 LATE IN THE NIGHT WEST OF HWY 52.
ANOTHER CONCERN TO WATCH IS A POTENTIAL WARM LAYER ACCOMPANYING THIS
SYSTEM. THE FASTEST 01.00Z NAM WOULD SUGGEST THAT THE PRECIPITATION
SUNDAY AFTERNOON OR EVENING WOULD START AS SLEET SAY IN THE AUSTIN
AREA. HOWEVER...SINCE A COMPROMISE APPROACH WAS FOLLOWED...ANY MIXED
PRECIPITATION TYPE TRANSITION ZONE SHOULD STAY OFF TO THE WEST.
.LONG TERM...MONDAY THROUGH THURSDAY NIGHT
308 AM CST FRI MAR 1 2013
MAIN CONCERN/FOCUS OF THE LONG TERM PERIOD REMAINS ON THE POTENT
UPPER TROUGH IN SOUTH DAKOTA EARLY MONDAY. THE 01.00Z
ECMWF/UKMET/CANADIAN AND GFS ENSEMBLES ARE ALL IN GOOD AGREEMENT
THAT THIS TROUGH WILL CLOSE OFF AND BE IN/NEAR WESTERN IOWA BY 12Z
TUESDAY. NOTE THAT THE 01.00Z GFS ALSO CLOSES IT OFF...BUT IS MUCH
MORE PROGRESSIVE...DOWN IN SOUTHERN MISSOURI AT 12Z TUESDAY. GIVEN
THE PREDOMINANCE OF SLOWER SOLUTIONS...DISCOUNTED THE GFS. THESE
SLOWER SOLUTIONS MEAN THAT A LOW TO MID-LEVEL FRONTOGENESIS BAND
WILL GET STUCK. WHEREVER THIS OCCURS THERE COULD END UP BEING SOME
DECENT SNOW ACCUMULATIONS. RIGHT NOW IT APPEARS THE BAND WOULD SET
UP FROM NORTH DAKOTA INTO SOUTHEAST MN AND INTO EASTERN IOWA. RAISED
PRECIPITATION CHANCES IN THIS AREA 20 PERCENT FROM THE PREVIOUS
FORECAST...AND MAY NEED TO BE RAISED MORE IF TRENDS CONTINUE.
A LONGWAVE TROUGH IS FORECAST TO TRY TO ENTER THE WEST COAST TUESDAY
NIGHT...WHICH MODELS HAVE SHOWN FOR AWHILE. THIS TROUGH WILL HELP
BUILD AND PUSH RIDGING EASTWARD...CAUSING THE UPPER LOW OVER WESTERN
IOWA TO SHIFT SOUTHEAST...AND PUSH THE LOW TO MID-LEVEL
FRONTOGENESIS CIRCULATION EASTWARD. THUS...THE SNOW MAY END UP
OVERSPREADING MUCH OF THE AREA ON TUESDAY AND ADDED 20-40 PERCENT
CHANCES AS A RESULT. EVEN ADDED A 20 PERCENT CHANCE OVER THE
SOUTHEAST 1/3 TUESDAY NIGHT.
WHEN ALL IS SAID AND DONE FROM THE SUNDAY NIGHT THROUGH TUESDAY
PERIOD...WE COULD BE LOOKING AT EITHER A LONG DURATION ADVISORY
EVENT OR EVEN WARNING IF THE 01.00Z CANADIAN ENDS UP RIGHT.
DEFINITELY NEED MODELS TO COME TO BETTER AGREEMENT AND MORE
DETAILS WORKED OUT BEFORE SPECULATING ON SNOWFALL AMOUNTS. 01.06Z
NAM CONTINUES TO SHOW AN AGGRESSIVE QPF SCENARIO SIMILAR TO THE
CANADIAN...ALONG WITH SPREADING PRECIPITATION FARTHER EAST. QUICK
LOOK AT THE 01.00Z ECMWF ENSEMBLE MEAN ALSO APPEARS TO BE IN-LINE
WITH THE NAM/CANADIAN IN TERMS OF 500MB HEIGHT AND MSLP. AS
MENTIONED...PLENTY OF DETAILS TO WORK OUT.
QUIET WEATHER ROUNDS OUT THE REST OF THE WEEK WITH MODELS IN GOOD
AGREEMENT SHIFTING THE UPPER RIDGE INTO THE FORECAST AREA. THIS
SHOULD BRING TEMPERATURES BACK UP TO NEAR OR POSSIBLY EVEN ABOVE
NORMAL BY THURSDAY. IF THE 01.00Z GFS IS CORRECT...WE COULD EVEN BE
LOOKING AT A RAIN/SNOW MIX THURSDAY NIGHT AS IT EJECTS OUT A
SHORTWAVE FROM THE WESTERN TROUGH THROUGH/NEARBY THE FORECAST AREA.
&&
.AVIATION...
1035 PM CST THU FEB 28 2013
LATEST FOG/STRATUS SATELLITE TRENDS ALONG WITH RAP RH FIELDS/BUFKIT
SOUNDINGS FAVOR HOLDING THE MVFR CIGS ACROSS KRST/KLSE EVEN LONGER
NOW...PERHAPS FOR MOST OF THE DAYTIME HOURS. NAM BUFKIT SOUNDINGS
SUGGEST THAT MIXING COULD START UP BY MID/LATE MORNING...HELPING TO
ELEVATE THE CIGS...ALTHOUGH NOT NECESSARILY SCATTERING THIS LOW DECK
OUT UNTIL LATER IN THE AFTERNOON. CONFIDENCE REMAINS SHAKY WHEN THIS
WILL OCCUR...BUT WILL CONTINUE TO PUSH TIMING BACK...TOWARD THESE
LATEST TRENDS. HIGH CLOUDS WILL LIKELY BE FILTERING BACK ACROSS THE
REGION EVEN AS THE LOW CLOUDS IF/WHEN VACATE TO THE
SOUTH...ASSOCIATED WITH A WEAK UPPER LEVEL DISTURBANCE.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
308 AM CST FRI MAR 1 2013
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...AJ
LONG TERM...AJ
AVIATION.....RIECK
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
1035 PM CST THU FEB 28 2013
.SHORT TERM...TONIGHT THROUGH SATURDAY NIGHT
315 PM CST THU FEB 28 2013
AT 3 PM...CLOUDS CONTINUE TO PIVOT AROUND A LOW PRESSURE SYSTEM
CENTERED OVER SOUTHEAST ONTARIO. HOWEVER SOME DRIER AIR FILTERING
INTO NORTHERN MINNESOTA...UPPER MICHIGAN...AND NORTHERN WISCONSIN
IS CAUSING SOME BREAKS TO DEVELOP IN THE MVFR DECK. BUFKIT SOUNDINGS
SUGGEST THAT THE CLOUDS WILL LINGER ACROSS THE FORECAST AREA
TONIGHT...AND THEN GRADUALLY BREAK UP FROM NORTHEAST TO SOUTHWEST
ON FRIDAY. AT THE SAME TIME...SOME MID AND HIGH CLOUDS WILL BE
MOVING INTO THE AREA FROM THE WEST AS A WEAKENING SHORT WAVE
/CURRENTLY OVER THE DAKOTAS/ MOVES EAST TOWARD THE FORECAST AREA.
WITH SKIES EXPECTED TO REMAIN CLOUDY TONIGHT...ONCE AGAIN WENT
HIGHER THAN THE MAV AND MET MOS TEMPERATURES. A 50-50 BLEND
OF LAST NIGHT/S MINIMUM TEMPERATURES AND THE BIAS CORRECTED
CONSALL...RAISED THE MINIMUM TEMPERATURES INTO THE MID AND
UPPER TEENS ACROSS NORTH-CENTRAL WISCONSIN...AND LOWER AND MID 20S
ACROSS THE REMAINDER OF THE FORECAST AREA. THIS SEEMS MUCH MORE
REALISTIC THAN THE MOS.
ALSO FOR TONIGHT...A WEAK 850-700 MB WILL MOVE SOUTH THROUGH
THE AREA TONIGHT. IN ADDITION...THERE IS SOME WEAK 275 ISENTROPIC
LIFT. SOUNDINGS SUGGEST THAT THE OMEGA ASSOCIATED WITH THIS
FEATURE WILL BE CO-LOCATED WITH THE LOW LEVEL MOISTURE. AS A
RESULT...KEPT SCATTERED FLURRIES IN THE FORECAST.
ON SATURDAY NIGHT...THE MODELS SHOW THAT A WEAKENING TROUGH WILL
MOVE INTO THE UPPER LEVEL RIDGE. WEAK TO MODERATE 280K ISENTROPIC
LIFT DEVELOPS AHEAD OF THIS TROUGH. THE 28.00Z NAM/WRF CONTINUES
TO SHOW SOME LIGHT PRECIPITATION ASSOCIATED WITH THIS SYSTEM.
THE ECMWF GENERATES SOME FLURRIES WITH THIS SYSTEM. MEANWHILE THE
GEM AND OPERATIONAL GFS KEEPS THE AREA DRY. LOOKING AT THE 12 GFS
MEMBERS...ONLY 3 OF THEM GENERATE ANY MEASURABLE PRECIPITATION.
THE MAIN DIFFERENCE BETWEEN THE GFS AND NAM IN THE BUFKIT
SOUNDINGS IS HOW THEY HANDLE THE DRY AIR BELOW 5K FEET. THE
NAM/WRF SATURATES THIS LAYER. MEANWHILE THE GFS SHOWS THAT THIS
LAYER WILL REMAIN VERY DRY. WITH UNCERTAINTIES IN THE LOW LEVEL
MOISTURE...JUST OPTED TO GO WITH FLURRIES AT THIS TIME.
.LONG TERM...SUNDAY THROUGH THURSDAY
315 PM CST THU FEB 28 2013
FROM LATE SUNDAY NIGHT INTO TUESDAY...THE MAIN FORECAST CONCERN IS
THE TRACK OF A LOW PRESSURE SYSTEM MOVING THROUGH THE REGION. BOTH
THE GFS AND ECMWF HAVE SHIFTED THE TRACK OF THIS LOW EVEN FURTHER
SOUTH OF ITS TRACK AT 28.00Z AND 28.06Z. WITH THIS TRACK...IT
WOULD ONLY AFFECT SOUTHEAST MINNESOTA AND NORTHEAST IOWA. MEANWHILE
THE GEM KEEPS THE SYSTEM TRACKING TO OUR NORTH. WITH THIS
TRACK...IT CONTINUES TO PRODUCE PRECIPITATION ACROSS THE ENTIRE
AREA. WITH THE MODELS STILL TRYING TO SORT OUT THINGS...OPTED TO
STAY WILL ALL BLEND FOR NOW.
BEYOND THIS TIME PERIOD...IT CONTINUES TO LOOK LIKE A 500 MB RIDGE
WILL DEVELOP ACROSS THE CENTRAL UNITED STATES. AS STATED
YESTERDAY...THIS IS ACTUALLY SUPPORTED BY MADDEN JULIAN
OSCILLATIONS FOR PHASES 6 AND 7. WHILE THERE IS AGREEMENT THAT
THIS RIDGE WILL BE BUILDING ACROSS THE AREA...THERE IS STILL SOME
UNCERTAINTY ON HOW WARM WE WILL GET.
&&
.AVIATION...
1035 PM CST THU FEB 28 2013
LATEST FOG/STRATUS SATELLITE TRENDS ALONG WITH RAP RH FIELDS/BUFKIT
SOUNDINGS FAVOR HOLDING THE MVFR CIGS ACROSS KRST/KLSE EVEN LONGER
NOW...PERHAPS FOR MOST OF THE DAYTIME HOURS. NAM BUFKIT SOUNDINGS
SUGGEST THAT MIXING COULD START UP BY MID/LATE MORNING...HELPING TO
ELEVATE THE CIGS...ALTHOUGH NOT NECESSARILY SCATTERING THIS LOW DECK
OUT UNTIL LATER IN THE AFTERNOON. CONFIDENCE REMAINS SHAKY WHEN THIS
WILL OCCUR...BUT WILL CONTINUE TO PUSH TIMING BACK...TOWARD THESE
LATEST TRENDS. HIGH CLOUDS WILL LIKELY BE FILTERING BACK ACROSS THE
REGION EVEN AS THE LOW CLOUDS IF/WHEN VACATE TO THE
SOUTH...ASSOCIATED WITH A WEAK UPPER LEVEL DISTURBANCE.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
228 PM CST THU FEB 28 2013
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...BOYNE
LONG TERM....BOYNE
AVIATION.....RIECK
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
951 AM CST FRI MAR 1 2013
.DISCUSSION...
919 AM CST
UPDATED THE GRIDS FOR THIS MORNING...MAINLY TO ACCOUNT FOR ONGOING
LAKE EFFECT SNOW SHOWERS.
LATEST RADAR IMAGERY DEPICTING SOME LIGHT RETURNS ACROSS ALL OF
NORTHERN ILLINOIS WITH AN ISOLATED AREA OF FAIRLY DECENT
RETURNS...PRIMARILY ACROSS SOUTHEAST COOK COUNTY AND NORTHWEST
LAKE COUNTY IN INDIANA. UNDER THE LIGHTER RETURNS LIGHT SNOW
CONTINUES WITH VIS STAYING CONFINED TO ONLY THE 3-6 MILE
RANGE...WITH VIS LIKELY AT OR UNDER 1 MILE UNDER THE STRONGER
RETURNS. THESE SNOW SHOWERS ARE IN RESPONSE TO PERSISTENT
NORTH/NORTHEAST FLOW OFF OF A MODERATELY UNSTABLE LAKE...AS WELL
AS WEAK LARGE SCALE LIFT. LATEST SURFACE ANALYSIS INDICATING A
SURFACE TROUGH SITUATED ACROSS THE SOUTHERN HALF OF THE
LAKE...EXTENDING BACK NORTHWEST FROM A WEAK SURFACE LOW OVER
IN/KY. THIS HAS RESULTED IN AN AREA OF BETTER CONVERGENCE THIS
MORNING...WHICH HAS THEN PROVIDED THIS ISOLATED AREA OF STRONGER
SNOW SHOWERS. LATEST SHORT TERM GUIDANCE IS INDICATING THIS TROUGH
TO SLOWLY EXIT/DAMPEN WITH ALL SURFACE WINDS BECOMING MORE
NORTHERLY...AND LOSS OF BETTER CONVERGENCE. SO DO EXPECT THIS
ISOLATED AREA OF STRONGER SNOW SHOWERS TO PERSIST OVER THE NEXT
COUPLE OF HOURS...ONCE AGAIN PRIMARILY AFFECTING ONLY SOUTHEAST
COOK AND NORTHWEST LAKE COUNTY IN INDIANA. UNDER THESE STRONGER
RETURNS IT WOULD NOT BE OUT OF THE QUESTION FOR SOME ADDITIONAL
ACCUMULATIONS...WITH 1 TO 3 INCHES NOT OF THE REALM OF
POSSIBILITY THROUGH MID DAY. LIGHT SNOW SHOWERS ARE THEN EXPECTED
TO CONTINUE INTO THE AFTERNOON...BUT WITH ONLY LIGHT ACCUMULATIONS
ANTICIPATED.
RODRIGUEZ
//PREV DISCUSSION...
330 AM CST
FORECAST CONCERNS ARE LAKE EFFECT SNOW SHOWER POTENTIAL THE NEXT FEW
DAYS...COLD TEMPERATURES OVER THE WEEKEND...AND A POSSIBLE SNOW
PRODUCING SYSTEM EARLY NEXT WEEK.
SHORT TERM...TODAY THROUGH SUNDAY NIGHT...
SLIGHTLY COLDER AIR MASS WILL SETTLE OVER THE REGION TODAY ON
CONTINUED NORTHERLY FLOW...WITH A LARGE AREA OF HIGH PRESSURE
BUILDING IN FROM THE NORTH. THIS SHOULD KEEP HIGHS A FEW DEGREES
COOLER THAN YESTERDAY. LAKE EFFECT SET UP IS QUITE MARGINAL
THERMODYNAMICALLY...BUT COMPENSATING SOMEWHAT WILL BE GOOD
CONVERGENCE AND FETCH WITH NORTH-NORTHEAST LOW LEVEL FLOW. THE
CONVERGENCE AND EVEN SOME ENHANCED LIFT IS BEST ALIGNED OVER
ILLINOIS AND PORTION OF NW INDIANA LAKEFRONT THROUGH MID/LATE
MORNING...SO BUMPED UP POPS SOME FROM PREVIOUS FORECAST. COULD SEE
SOME VERY LIGHT ACCUMULATIONS. OUTSIDE OF LAKE EFFECT...THERE MAY BE
SOME FLURRIES INLAND. ALTHOUGH STRATUS CAN CLEAR OUT QUICKER THIS
TIME OF YEAR DUE TO HIGHER SUN ANGLE...THINK THE NAM IS BEING WAY
TOO AGGRESSIVE WITH CLEARING TREND FROM NORTH. USED RAP GUIDANCE FOR
NEAR TERM SKY FORECAST. MOST OF CWA SHOULD SEE OVC THROUGH DAYLIGHT
HOURS.
THE SAME GENERAL IDEA OF DECENT CONVERGENCE BUT VERY MARGINAL
THERMODYNAMICS AND INVERSION HEIGHTS CONTINUES THROUGH SATURDAY WITH
THE LAKE EFFECT. WILL CONTINUE TO CARRY CHANCE POPS...THOUGH THEY
WILL SLIDE INTO NW INDIANA ON SATURDAY AS NORTHERLY FLOW BECOMES
JUST WEST OF DUE NORTH. SKIES SHOULD START TO CLEAR BY DAYBREAK OVER
THE NW CWA...SO TEMPERATURES SHOULD DROP PRETTY WELL THERE GIVEN
THE GOOD RADIATION COOLING...PROBABLY INTO THE MID TEENS.
OUTSIDE OF LAKE EFFECT CONCERNS...THE ONLY FOCUS OVER THE WEEKEND
WAS TEMPERATURES WITH HIGH PRESSURE BUILDING OVERHEAD. FOR HIGHS
ON SATURDAY...SUSPECT THAT THE MARCH SUN WILL GO TO WORK ON THE
SNOW COVER...ESPECIALLY FOR AREAS THAT DIDNT SEE MUCH THIS WEEK.
FOR MARCH 1-15...WITH 850 TEMPS AROUND -10C AS IS PROGGED ON
SATURDAY...MEDIAN HIGH AT ORD IS 34 DEGREES. WENT JUST UNDER THAT
IN NORTHERN CWA/ESPECIALLY IN THE NORTHEAST WHERE SNOW PACK IS
DEEPEST...YIELDING HIGHS AROUND 30. TO THE SOUTH OF I-80...SUSPECT
WE`LL SEE SOME MID TO EVEN UPPER 30S AS SUN EATS AWAY AT MEAGER
SNOW COVER.
THEN SUNDAY NIGHT...THERE IS A STRONG SIGNAL FOR GOOD RADIATIONAL
COOLING...ESPECIALLY ON THE ECMWF...WHICH MAY BE A BIT TOO
AGGRESSIVE WITH ITS ZERO TO SLIGHTLY BELOW ZERO NUMBERS FOR NORTH
CENTRAL IL. BASICALLY CONTINUED IDEA OF PREVIOUS FORECAST WITH
POTENTIAL FOR SINGLE DIGIT LOWS WEST OF FOX RIVER. ON SUNDAY...THE
COLD START MAY KEEP TEMPS IN CHECK SOMEWHAT...BUT MARCH SUN ANGLE
AND LONGER DAYLIGHT HOURS EXPECTED TO COMPENSATE...IN ADDITION TO
SLIGHTLY WARMER TEMPS ALOFT. MEDIAN ORD HIGHS FOR DAYS WITH 850
TEMPS AS PROGGED ON SUNDAY IN -6 TO -8 RANGE IS 38. DIDNT GO THIS
MILD DUE TO COLD START AND SNOW COVER OVER NORTHERN CWA...BUT
BUMPED UP TEMPS A FEW DEGREES FROM PREVIOUS. IF SNOW COVER CAN BE
ELIMINATED ON SATURDAY OVER SOUTH...WOULDNT BE SURPRISED IF SOME
LOCATIONS TAG 40 DEGREES...BUT FOR NOW WENT WITH UPPER 30S IN
CENTRAL IL. INCREASING CLOUD COVER SHOULD RESULT IN LOWS SEVERAL
DEGREES WARMER SUNDAY NIGHT THAN SATURDAY NIGHT.
LONG TERM...MONDAY THROUGH THURSDAY
MAIN FOCUS IS ON VERY ENERGETIC CLIPPER SYSTEM EARLY NEXT WEEK.
THERE HAVE BEEN FAIRLY SIGNIFICANT RUN TO RUN CHANGES WITH THE
TIMING AND TRACK OF THE STRONG UPPER LOW AND SURFACE REFLECTION.
WOULD EXPECT THIS TO CONTINUE UNTIL UPPER WAVE MAKES LANDFALL IN
PACIFIC NORTHWEST SATURDAY NIGHT ALLOWING FOR SAMPLING BY RAOB
NETWORK. AS IT STANDS RIGHT NOW...00Z GUIDANCE HAS SHIFTED BACK
NORTH...WHICH WOULD PUT MOST OF CWA IN LINE FOR A POTENTIALLY
ACCUMULATING SNOW. COULD SEE THE START OF SOME WAA SNOWS AHEAD OF
SYSTEM ON MONDAY...SO BLENDED POPS WERE MAINTAINED.
HOWEVER...BIGGEST CHANGE WAS TO GREATLY INCREASE POPS ABOVE
ALLBLEND MONDAY NIGHT AND TUESDAY IN LINE WITH A SLOWER
PROGRESSION OF THE UPPER LOW AND ATTENDANT SURFACE LOW FAVORED BY
THE 00Z ECMWF...CANADIAN...GEFS AND HPC. GFS APPEARS MUCH TOO FAST
IN CLEARING THE SYSTEM OFF TO THE EAST. FOR NOW...BUMPED UP POPS
TO MID RANGE CHANCE GIVEN UNCERTAINTY.
AS CURRENTLY MODELED...THE UPPER LOW WITH THIS SYSTEM LOOKS QUITE
STRONG...WITH A TIGHT BAROCLINIC ZONE ALONG/AHEAD OF ITS TRACK. THUS
THERE COULD BE A NICE SWATH OF SNOW PUT DOWN SOMEWHERE OVER/NEAR THE
REGION. ON THE NEGATIVE SIDE...TEMPERATURES AS IS USUALLY THE CASE
IN MARCH WOULD BE NEAR FREEZING...SO THE SNOW WOULD HAVE TO COME
DOWN HARD TO ACCUMULATE EFFICIENTLY. LOTS OF TIME TO MONITOR THIS
SYSTEM.
FOR THE REST OF THE EXTENDED AND BEYOND...AFTER A FAIRLY COOL DAY ON
WEDNESDAY BEHIND THE EARLY WEEK SYSTEM...THERE COULD BE BRIEF WARM UP
TO NORMAL TO ABOVE NORMAL AS THE PATTERN TRANSITIONS FROM AN EASTERN
TROUGH/WESTERN RIDGE (POSITIVE PNA) CONFIGURATION TO A WESTERN
TROUGH/EASTERN RIDGE (NEGATIVE PNA) PATTERN. WITH RIDGING FIRST
AMPLIFYING INTO CENTER OF CONUS...WE COULD SEE A FEW DAYS OF
TEMPERATURES AT LEAST BACK INTO THE 40S.
HOWEVER...THE LONG RANGE ENSEMBLES LOOKING BEYOND THIS 7 DAY
FORECAST PERIOD ARE HOLDING ONTO THE IDEA OF MAINTAINING HIGH
LATITUDE BLOCKING/NEGATIVE NAO AND NEGATIVE AO THROUGH MID MARCH.
IN ADDITION...RIDGING MAY AMPLIFY OVER OR NEAR ALASKA WHICH ALLOWS
FRESH COLD AIR TO INFILTRATE CANADA AND THE NORTHERN CONUS. BOTTOM
LINE IS ANY WARM UP COULD BE QUICKLY FOLLOWED BY A RETURN TO THE
COLDER THAN NORMAL PATTERN. NO MARCH 2012 PATTERN IS SEEN IN THE
EXTENDED FOR ANYONE HOPING FOR AN EARLY SUMMER AGAIN.
RC
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 16Z...
* SCT LAKE EFFECT SHSN...VIS BRIEFLY DROPPING DOWN IN THE 2 TO 3
SM RANGE IN THE HEAVIER SHOWERS...ESPECIALLY THIS MORNING. SNOW
SHOWERS AND FLURRIES MAY CONTINUE THIS AFTERNOON BUT WILL BE LESS
ROBUST THAN THE CURRENT ACTIVITY.
* NNW WINDS TO TRANSITION TO N-NE BY EARLY AFTERNOON
KB
//DISCUSSION...UPDATED 12Z...
EXTENSIVE HIGH END MVFR/LOW END VFR STRATUS DECK BLANKETS THE
REGION WITH SOME POCKETS OF FLURRIES LIKELY TO TO PERSIST THRU
TODAY. LAKE EFFECT FLURRIES AND SCATTERED SNOW SHOWERS WILL
CONTINUE AT LEAST THROUGH THE EARLY AFTERNOON INTO CHGO AREA...AND
POSSIBLY INTO THIS EVENING. SMALL THREAT OF SOME BRIEF VSBY
REDUCTIONS IN -SHSN THIS MORNING...BUT PROBABLY NOT BELOW 3SM WITH
CIGS LIKELY TO BE GENERALLY AT OR ABOVE 1500FT. LAND BREEZE
INFLUENCE TO WIND DIRECTION SHOULD RESULT IN WINDS BEING WEST OF
DUE NORTH WINDS EARLY THIS MORNING AT CHGO AREA TERMINALS WITH
TRANSITION TO MORE NE WINDS EXPECTED LATER THIS MORNING.
IZZI
//ORD AND MDW CONFIDENCE...UPDATED 16Z...
* MEDIUM CONFIDENCE IN SHSN WITH BRIEF PERIODS OF 2 TO 3 SM VIS.
* HIGH CONFIDENCE IN WIND SHIFT TO N-NE...BUT LOW CONFIDENCE IN
EXACT TIMING
* MEDIUM/HIGH CONFIDENCE IN CIGS FORECAST THROUGH THE PERIOD
KB
//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...
SATURDAY NIGHT...MVFR CIGS POSSIBLE EARLY.
SUNDAY...VFR.
MONDAY...CHANCE OF LIGHT SNOW IN THE AFTERNOON. MVFR POSSIBLE
LATE.
MONDAY NIGHT INTO TUESDAY...GOOD CHANCE OF SNOW. IFR PROBABLE.
WEDNESDAY...MVFR CIGS POSSIBLE.
THURSDAY...VFR EXPECTED.
IZZI
&&
.MARINE...
222 AM CST
MODERATELY STRONG NORTH WINDS LIKELY TO CONTINUE THROUGH SATURDAY
WITH OCCASIONAL GALE FORCE GUSTS A POSSIBILITY...ESPECIALLY LATER
THIS AFTERNOON INTO THE EVENING...BUT GENERALLY THINK ANY GALES
WILL BE INFREQUENT ENOUGH TO KEEP OUT OF THE FORECAST. WINDS WILL
BEGIN TO DIMINISHING LATER SATURDAY INTO SUNDAY AS RIDGE AXIS
APPROACHES AND THEN MOVES ACROSS THE LAKE SUNDAY NIGHT. ANOTHER
SYSTEM WILL PASS TO THE SOUTHWEST OF THE LAKE EARLY/MIDDLE PART OF
NEXT WEEK WITH WINDS FRESHENING UP A BIT...BUT SYSTEM SHOULD BE
WEAK ENOUGH AND FAR ENOUGH AWAY TO NOT CAUSE ANY MAJOR
WINDS/WAVES.
IZZI
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL 3 AM
SUNDAY.
SMALL CRAFT ADVISORY...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL 9 AM SUNDAY.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
935 AM CST FRI MAR 1 2013
.DISCUSSION...
919 AM CST
UPDATED THE GRIDS FOR THIS MORNING...MAINLY TO ACCOUNT FOR ONGOING
LAKE EFFECT SNOW SHOWERS.
LATEST RADAR IMAGERY DEPICTING SOME LIGHT RETURNS ACROSS ALL OF
NORTHERN ILLINOIS WITH AN ISOLATED AREA OF FAIRLY DECENT
RETURNS...PRIMARILY ACROSS SOUTHEAST COOK COUNTY AND NORTHWEST
LAKE COUNTY IN INDIANA. UNDER THE LIGHTER RETURNS LIGHT SNOW
CONTINUES WITH VIS STAYING CONFINED TO ONLY THE 3-6 MILE
RANGE...WITH VIS LIKELY AT OR UNDER 1 MILE UNDER THE STRONGER
RETURNS. THESE SNOW SHOWERS ARE IN RESPONSE TO PERSISTENT
NORTH/NORTHEAST FLOW OFF OF A MODERATELY UNSTABLE LAKE...AS WELL
AS WEAK LARGE SCALE LIFT. LATEST SURFACE ANALYSIS INDICATING A
SURFACE TROUGH SITUATED ACROSS THE SOUTHERN HALF OF THE
LAKE...EXTENDING BACK NORTHWEST FROM A WEAK SURFACE LOW OVER
IN/KY. THIS HAS RESULTED IN AN AREA OF BETTER CONVERGENCE THIS
MORNING...WHICH HAS THEN PROVIDED THIS ISOLATED AREA OF STRONGER
SNOW SHOWERS. LATEST SHORT TERM GUIDANCE IS INDICATING THIS TROUGH
TO SLOWLY EXIT/DAMPEN WITH ALL SURFACE WINDS BECOMING MORE
NORTHERLY...AND LOSS OF BETTER CONVERGENCE. SO DO EXPECT THIS
ISOLATED AREA OF STRONGER SNOW SHOWERS TO PERSIST OVER THE NEXT
COUPLE OF HOURS...ONCE AGAIN PRIMARILY AFFECTING ONLY SOUTHEAST
COOK AND NORTHWEST LAKE COUNTY IN INDIANA. UNDER THESE STRONGER
RETURNS IT WOULD NOT BE OUT OF THE QUESTION FOR SOME ADDITIONAL
ACCUMULATIONS...WITH 1 TO 3 INCHES NOT OF THE REALM OF
POSSIBILITY THROUGH MID DAY. LIGHT SNOW SHOWERS ARE THEN EXPECTED
TO CONTINUE INTO THE AFTERNOON...BUT WITH ONLY LIGHT ACCUMULATIONS
ANTICIPATED.
RODRIGUEZ
&&
.PREV DISCUSSION...
330 AM CST
FORECAST CONCERNS ARE LAKE EFFECT SNOW SHOWER POTENTIAL THE NEXT FEW
DAYS...COLD TEMPERATURES OVER THE WEEKEND...AND A POSSIBLE SNOW
PRODUCING SYSTEM EARLY NEXT WEEK.
SHORT TERM...TODAY THROUGH SUNDAY NIGHT...
SLIGHTLY COLDER AIR MASS WILL SETTLE OVER THE REGION TODAY ON
CONTINUED NORTHERLY FLOW...WITH A LARGE AREA OF HIGH PRESSURE
BUILDING IN FROM THE NORTH. THIS SHOULD KEEP HIGHS A FEW DEGREES
COOLER THAN YESTERDAY. LAKE EFFECT SET UP IS QUITE MARGINAL
THERMODYNAMICALLY...BUT COMPENSATING SOMEWHAT WILL BE GOOD
CONVERGENCE AND FETCH WITH NORTH-NORTHEAST LOW LEVEL FLOW. THE
CONVERGENCE AND EVEN SOME ENHANCED LIFT IS BEST ALIGNED OVER
ILLINOIS AND PORTION OF NW INDIANA LAKEFRONT THROUGH MID/LATE
MORNING...SO BUMPED UP POPS SOME FROM PREVIOUS FORECAST. COULD SEE
SOME VERY LIGHT ACCUMULATIONS. OUTSIDE OF LAKE EFFECT...THERE MAY BE
SOME FLURRIES INLAND. ALTHOUGH STRATUS CAN CLEAR OUT QUICKER THIS
TIME OF YEAR DUE TO HIGHER SUN ANGLE...THINK THE NAM IS BEING WAY
TOO AGGRESSIVE WITH CLEARING TREND FROM NORTH. USED RAP GUIDANCE FOR
NEAR TERM SKY FORECAST. MOST OF CWA SHOULD SEE OVC THROUGH DAYLIGHT
HOURS.
THE SAME GENERAL IDEA OF DECENT CONVERGENCE BUT VERY MARGINAL
THERMODYNAMICS AND INVERSION HEIGHTS CONTINUES THROUGH SATURDAY WITH
THE LAKE EFFECT. WILL CONTINUE TO CARRY CHANCE POPS...THOUGH THEY
WILL SLIDE INTO NW INDIANA ON SATURDAY AS NORTHERLY FLOW BECOMES
JUST WEST OF DUE NORTH. SKIES SHOULD START TO CLEAR BY DAYBREAK OVER
THE NW CWA...SO TEMPERATURES SHOULD DROP PRETTY WELL THERE GIVEN
THE GOOD RADIATION COOLING...PROBABLY INTO THE MID TEENS.
OUTSIDE OF LAKE EFFECT CONCERNS...THE ONLY FOCUS OVER THE WEEKEND
WAS TEMPERATURES WITH HIGH PRESSURE BUILDING OVERHEAD. FOR HIGHS
ON SATURDAY...SUSPECT THAT THE MARCH SUN WILL GO TO WORK ON THE
SNOW COVER...ESPECIALLY FOR AREAS THAT DIDNT SEE MUCH THIS WEEK.
FOR MARCH 1-15...WITH 850 TEMPS AROUND -10C AS IS PROGGED ON
SATURDAY...MEDIAN HIGH AT ORD IS 34 DEGREES. WENT JUST UNDER THAT
IN NORTHERN CWA/ESPECIALLY IN THE NORTHEAST WHERE SNOW PACK IS
DEEPEST...YIELDING HIGHS AROUND 30. TO THE SOUTH OF I-80...SUSPECT
WE`LL SEE SOME MID TO EVEN UPPER 30S AS SUN EATS AWAY AT MEAGER
SNOW COVER.
THEN SUNDAY NIGHT...THERE IS A STRONG SIGNAL FOR GOOD RADIATIONAL
COOLING...ESPECIALLY ON THE ECMWF...WHICH MAY BE A BIT TOO
AGGRESSIVE WITH ITS ZERO TO SLIGHTLY BELOW ZERO NUMBERS FOR NORTH
CENTRAL IL. BASICALLY CONTINUED IDEA OF PREVIOUS FORECAST WITH
POTENTIAL FOR SINGLE DIGIT LOWS WEST OF FOX RIVER. ON SUNDAY...THE
COLD START MAY KEEP TEMPS IN CHECK SOMEWHAT...BUT MARCH SUN ANGLE
AND LONGER DAYLIGHT HOURS EXPECTED TO COMPENSATE...IN ADDITION TO
SLIGHTLY WARMER TEMPS ALOFT. MEDIAN ORD HIGHS FOR DAYS WITH 850
TEMPS AS PROGGED ON SUNDAY IN -6 TO -8 RANGE IS 38. DIDNT GO THIS
MILD DUE TO COLD START AND SNOW COVER OVER NORTHERN CWA...BUT
BUMPED UP TEMPS A FEW DEGREES FROM PREVIOUS. IF SNOW COVER CAN BE
ELIMINATED ON SATURDAY OVER SOUTH...WOULDNT BE SURPRISED IF SOME
LOCATIONS TAG 40 DEGREES...BUT FOR NOW WENT WITH UPPER 30S IN
CENTRAL IL. INCREASING CLOUD COVER SHOULD RESULT IN LOWS SEVERAL
DEGREES WARMER SUNDAY NIGHT THAN SATURDAY NIGHT.
LONG TERM...MONDAY THROUGH THURSDAY
MAIN FOCUS IS ON VERY ENERGETIC CLIPPER SYSTEM EARLY NEXT WEEK.
THERE HAVE BEEN FAIRLY SIGNIFICANT RUN TO RUN CHANGES WITH THE
TIMING AND TRACK OF THE STRONG UPPER LOW AND SURFACE REFLECTION.
WOULD EXPECT THIS TO CONTINUE UNTIL UPPER WAVE MAKES LANDFALL IN
PACIFIC NORTHWEST SATURDAY NIGHT ALLOWING FOR SAMPLING BY RAOB
NETWORK. AS IT STANDS RIGHT NOW...00Z GUIDANCE HAS SHIFTED BACK
NORTH...WHICH WOULD PUT MOST OF CWA IN LINE FOR A POTENTIALLY
ACCUMULATING SNOW. COULD SEE THE START OF SOME WAA SNOWS AHEAD OF
SYSTEM ON MONDAY...SO BLENDED POPS WERE MAINTAINED.
HOWEVER...BIGGEST CHANGE WAS TO GREATLY INCREASE POPS ABOVE
ALLBLEND MONDAY NIGHT AND TUESDAY IN LINE WITH A SLOWER
PROGRESSION OF THE UPPER LOW AND ATTENDANT SURFACE LOW FAVORED BY
THE 00Z ECMWF...CANADIAN...GEFS AND HPC. GFS APPEARS MUCH TOO FAST
IN CLEARING THE SYSTEM OFF TO THE EAST. FOR NOW...BUMPED UP POPS
TO MID RANGE CHANCE GIVEN UNCERTAINTY.
AS CURRENTLY MODELED...THE UPPER LOW WITH THIS SYSTEM LOOKS QUITE
STRONG...WITH A TIGHT BAROCLINIC ZONE ALONG/AHEAD OF ITS TRACK. THUS
THERE COULD BE A NICE SWATH OF SNOW PUT DOWN SOMEWHERE OVER/NEAR THE
REGION. ON THE NEGATIVE SIDE...TEMPERATURES AS IS USUALLY THE CASE
IN MARCH WOULD BE NEAR FREEZING...SO THE SNOW WOULD HAVE TO COME
DOWN HARD TO ACCUMULATE EFFICIENTLY. LOTS OF TIME TO MONITOR THIS
SYSTEM.
FOR THE REST OF THE EXTENDED AND BEYOND...AFTER A FAIRLY COOL DAY ON
WEDNESDAY BEHIND THE EARLY WEEK SYSTEM...THERE COULD BE BRIEF WARM UP
TO NORMAL TO ABOVE NORMAL AS THE PATTERN TRANSITIONS FROM AN EASTERN
TROUGH/WESTERN RIDGE (POSITIVE PNA) CONFIGURATION TO A WESTERN
TROUGH/EASTERN RIDGE (NEGATIVE PNA) PATTERN. WITH RIDGING FIRST
AMPLIFYING INTO CENTER OF CONUS...WE COULD SEE A FEW DAYS OF
TEMPERATURES AT LEAST BACK INTO THE 40S.
HOWEVER...THE LONG RANGE ENSEMBLES LOOKING BEYOND THIS 7 DAY
FORECAST PERIOD ARE HOLDING ONTO THE IDEA OF MAINTAINING HIGH
LATITUDE BLOCKING/NEGATIVE NAO AND NEGATIVE AO THROUGH MID MARCH.
IN ADDITION...RIDGING MAY AMPLIFY OVER OR NEAR ALASKA WHICH ALLOWS
FRESH COLD AIR TO INFILTRATE CANADA AND THE NORTHERN CONUS. BOTTOM
LINE IS ANY WARM UP COULD BE QUICKLY FOLLOWED BY A RETURN TO THE
COLDER THAN NORMAL PATTERN. NO MARCH 2012 PATTERN IS SEEN IN THE
EXTENDED FOR ANYONE HOPING FOR AN EARLY SUMMER AGAIN.
RC
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 14Z...
* FLURRIES WITH SCT LAKE EFFECT SHSN...VIS BRIEFLY DROPPING DOWN IN
THE 2 TO 3 SM RANGE IN THE HEAVIER SHOWERS...ESPECIALLY THIS
MORNING.
* NNW WINDS TO TRANSITION TO N-NE BY LATE MORNING/EARLY AFTERNOON
IZZI/KB
//DISCUSSION...UPDATED 12Z...
EXTENSIVE HIGH END MVFR/LOW END VFR STRATUS DECK BLANKETS THE
REGION WITH SOME POCKETS OF FLURRIES LIKELY TO TO PERSIST THRU
TODAY. LAKE EFFECT FLURRIES AND SCATTERED SNOW SHOWERS WILL
CONTINUE AT LEAST THROUGH THE EARLY AFTERNOON INTO CHGO AREA...AND
POSSIBLY INTO THIS EVENING. SMALL THREAT OF SOME BRIEF VSBY
REDUCTIONS IN -SHSN THIS MORNING...BUT PROBABLY NOT BELOW 3SM WITH
CIGS LIKELY TO BE GENERALLY AT OR ABOVE 1500FT. LAND BREEZE
INFLUENCE TO WIND DIRECTION SHOULD RESULT IN WINDS BEING WEST OF
DUE NORTH WINDS EARLY THIS MORNING AT CHGO AREA TERMINALS WITH
TRANSITION TO MORE NE WINDS EXPECTED LATER THIS MORNING.
IZZI
//ORD AND MDW CONFIDENCE...UPDATED 14Z...
* MEDIUM CONFIDENCE IN SHSN WITH BRIEF PERIODS OF 2 TO 3 SM VIS.
* HIGH CONFIDENCE IN WIND SHIFT TO N-NE...BUT LOW CONFIDENCE IN
EXACT TIMING
* MEDIUM/HIGH CONFIDENCE IN CIGS FORECAST THROUGH THE PERIOD
IZZI/KB
//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...
SATURDAY NIGHT...MVFR CIGS POSSIBLE EARLY.
SUNDAY...VFR.
MONDAY...CHANCE OF LIGHT SNOW IN THE AFTERNOON. MVFR POSSIBLE
LATE.
MONDAY NIGHT INTO TUESDAY...GOOD CHANCE OF SNOW. IFR PROBABLE.
WEDNESDAY...MVFR CIGS POSSIBLE.
THURSDAY...VFR EXPECTED.
IZZI
&&
.MARINE...
222 AM CST
MODERATELY STRONG NORTH WINDS LIKELY TO CONTINUE THROUGH SATURDAY
WITH OCCASIONAL GALE FORCE GUSTS A POSSIBILITY...ESPECIALLY LATER
THIS AFTERNOON INTO THE EVENING...BUT GENERALLY THINK ANY GALES
WILL BE INFREQUENT ENOUGH TO KEEP OUT OF THE FORECAST. WINDS WILL
BEGIN TO DIMINISHING LATER SATURDAY INTO SUNDAY AS RIDGE AXIS
APPROACHES AND THEN MOVES ACROSS THE LAKE SUNDAY NIGHT. ANOTHER
SYSTEM WILL PASS TO THE SOUTHWEST OF THE LAKE EARLY/MIDDLE PART OF
NEXT WEEK WITH WINDS FRESHENING UP A BIT...BUT SYSTEM SHOULD BE
WEAK ENOUGH AND FAR ENOUGH AWAY TO NOT CAUSE ANY MAJOR
WINDS/WAVES.
IZZI
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL 3 AM
SUNDAY.
SMALL CRAFT ADVISORY...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL 9 AM SUNDAY.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
810 AM CST FRI MAR 1 2013
.DISCUSSION...
330 AM CST
FORECAST CONCERNS ARE LAKE EFFECT SNOW SHOWER POTENTIAL THE NEXT FEW
DAYS...COLD TEMPERATURES OVER THE WEEKEND...AND A POSSIBLE SNOW
PRODUCING SYSTEM EARLY NEXT WEEK.
SHORT TERM...TODAY THROUGH SUNDAY NIGHT...
SLIGHTLY COLDER AIR MASS WILL SETTLE OVER THE REGION TODAY ON
CONTINUED NORTHERLY FLOW...WITH A LARGE AREA OF HIGH PRESSURE
BUILDING IN FROM THE NORTH. THIS SHOULD KEEP HIGHS A FEW DEGREES
COOLER THAN YESTERDAY. LAKE EFFECT SET UP IS QUITE MARGINAL
THERMODYNAMICALLY...BUT COMPENSATING SOMEWHAT WILL BE GOOD
CONVERGENCE AND FETCH WITH NORTH-NORTHEAST LOW LEVEL FLOW. THE
CONVERGENCE AND EVEN SOME ENHANCED LIFT IS BEST ALIGNED OVER
ILLINOIS AND PORTION OF NW INDIANA LAKEFRONT THROUGH MID/LATE
MORNING...SO BUMPED UP POPS SOME FROM PREVIOUS FORECAST. COULD SEE
SOME VERY LIGHT ACCUMULATIONS. OUTSIDE OF LAKE EFFECT...THERE MAY BE
SOME FLURRIES INLAND. ALTHOUGH STRATUS CAN CLEAR OUT QUICKER THIS
TIME OF YEAR DUE TO HIGHER SUN ANGLE...THINK THE NAM IS BEING WAY
TOO AGGRESSIVE WITH CLEARING TREND FROM NORTH. USED RAP GUIDANCE FOR
NEAR TERM SKY FORECAST. MOST OF CWA SHOULD SEE OVC THROUGH DAYLIGHT
HOURS.
THE SAME GENERAL IDEA OF DECENT CONVERGENCE BUT VERY MARGINAL
THERMODYNAMICS AND INVERSION HEIGHTS CONTINUES THROUGH SATURDAY WITH
THE LAKE EFFECT. WILL CONTINUE TO CARRY CHANCE POPS...THOUGH THEY
WILL SLIDE INTO NW INDIANA ON SATURDAY AS NORTHERLY FLOW BECOMES
JUST WEST OF DUE NORTH. SKIES SHOULD START TO CLEAR BY DAYBREAK OVER
THE NW CWA...SO TEMPERATURES SHOULD DROP PRETTY WELL THERE GIVEN
THE GOOD RADIATION COOLING...PROBABLY INTO THE MID TEENS.
OUTSIDE OF LAKE EFFECT CONCERNS...THE ONLY FOCUS OVER THE WEEKEND
WAS TEMPERATURES WITH HIGH PRESSURE BUILDING OVERHEAD. FOR HIGHS
ON SATURDAY...SUSPECT THAT THE MARCH SUN WILL GO TO WORK ON THE
SNOW COVER...ESPECIALLY FOR AREAS THAT DIDNT SEE MUCH THIS WEEK.
FOR MARCH 1-15...WITH 850 TEMPS AROUND -10C AS IS PROGGED ON
SATURDAY...MEDIAN HIGH AT ORD IS 34 DEGREES. WENT JUST UNDER THAT
IN NORTHERN CWA/ESPECIALLY IN THE NORTHEAST WHERE SNOW PACK IS
DEEPEST...YIELDING HIGHS AROUND 30. TO THE SOUTH OF I-80...SUSPECT
WE`LL SEE SOME MID TO EVEN UPPER 30S AS SUN EATS AWAY AT MEAGER
SNOW COVER.
THEN SUNDAY NIGHT...THERE IS A STRONG SIGNAL FOR GOOD RADIATIONAL
COOLING...ESPECIALLY ON THE ECMWF...WHICH MAY BE A BIT TOO
AGGRESSIVE WITH ITS ZERO TO SLIGHTLY BELOW ZERO NUMBERS FOR NORTH
CENTRAL IL. BASICALLY CONTINUED IDEA OF PREVIOUS FORECAST WITH
POTENTIAL FOR SINGLE DIGIT LOWS WEST OF FOX RIVER. ON SUNDAY...THE
COLD START MAY KEEP TEMPS IN CHECK SOMEWHAT...BUT MARCH SUN ANGLE
AND LONGER DAYLIGHT HOURS EXPECTED TO COMPENSATE...IN ADDITION TO
SLIGHTLY WARMER TEMPS ALOFT. MEDIAN ORD HIGHS FOR DAYS WITH 850
TEMPS AS PROGGED ON SUNDAY IN -6 TO -8 RANGE IS 38. DIDNT GO THIS
MILD DUE TO COLD START AND SNOW COVER OVER NORTHERN CWA...BUT
BUMPED UP TEMPS A FEW DEGREES FROM PREVIOUS. IF SNOW COVER CAN BE
ELIMINATED ON SATURDAY OVER SOUTH...WOULDNT BE SURPRISED IF SOME
LOCATIONS TAG 40 DEGREES...BUT FOR NOW WENT WITH UPPER 30S IN
CENTRAL IL. INCREASING CLOUD COVER SHOULD RESULT IN LOWS SEVERAL
DEGREES WARMER SUNDAY NIGHT THAN SATURDAY NIGHT.
LONG TERM...MONDAY THROUGH THURSDAY
MAIN FOCUS IS ON VERY ENERGETIC CLIPPER SYSTEM EARLY NEXT WEEK.
THERE HAVE BEEN FAIRLY SIGNIFICANT RUN TO RUN CHANGES WITH THE
TIMING AND TRACK OF THE STRONG UPPER LOW AND SURFACE REFLECTION.
WOULD EXPECT THIS TO CONTINUE UNTIL UPPER WAVE MAKES LANDFALL IN
PACIFIC NORTHWEST SATURDAY NIGHT ALLOWING FOR SAMPLING BY RAOB
NETWORK. AS IT STANDS RIGHT NOW...00Z GUIDANCE HAS SHIFTED BACK
NORTH...WHICH WOULD PUT MOST OF CWA IN LINE FOR A POTENTIALLY
ACCUMULATING SNOW. COULD SEE THE START OF SOME WAA SNOWS AHEAD OF
SYSTEM ON MONDAY...SO BLENDED POPS WERE MAINTAINED.
HOWEVER...BIGGEST CHANGE WAS TO GREATLY INCREASE POPS ABOVE
ALLBLEND MONDAY NIGHT AND TUESDAY IN LINE WITH A SLOWER
PROGRESSION OF THE UPPER LOW AND ATTENDANT SURFACE LOW FAVORED BY
THE 00Z ECMWF...CANADIAN...GEFS AND HPC. GFS APPEARS MUCH TOO FAST
IN CLEARING THE SYSTEM OFF TO THE EAST. FOR NOW...BUMPED UP POPS
TO MID RANGE CHANCE GIVEN UNCERTAINTY.
AS CURRENTLY MODELED...THE UPPER LOW WITH THIS SYSTEM LOOKS QUITE
STRONG...WITH A TIGHT BAROCLINIC ZONE ALONG/AHEAD OF ITS TRACK. THUS
THERE COULD BE A NICE SWATH OF SNOW PUT DOWN SOMEWHERE OVER/NEAR THE
REGION. ON THE NEGATIVE SIDE...TEMPERATURES AS IS USUALLY THE CASE
IN MARCH WOULD BE NEAR FREEZING...SO THE SNOW WOULD HAVE TO COME
DOWN HARD TO ACCUMULATE EFFICIENTLY. LOTS OF TIME TO MONITOR THIS
SYSTEM.
FOR THE REST OF THE EXTENDED AND BEYOND...AFTER A FAIRLY COOL DAY ON
WEDNESDAY BEHIND THE EARLY WEEK SYSTEM...THERE COULD BE BRIEF WARM UP
TO NORMAL TO ABOVE NORMAL AS THE PATTERN TRANSITIONS FROM AN EASTERN
TROUGH/WESTERN RIDGE (POSITIVE PNA) CONFIGURATION TO A WESTERN
TROUGH/EASTERN RIDGE (NEGATIVE PNA) PATTERN. WITH RIDGING FIRST
AMPLIFYING INTO CENTER OF CONUS...WE COULD SEE A FEW DAYS OF
TEMPERATURES AT LEAST BACK INTO THE 40S.
HOWEVER...THE LONG RANGE ENSEMBLES LOOKING BEYOND THIS 7 DAY
FORECAST PERIOD ARE HOLDING ONTO THE IDEA OF MAINTAINING HIGH
LATITUDE BLOCKING/NEGATIVE NAO AND NEGATIVE AO THROUGH MID MARCH.
IN ADDITION...RIDGING MAY AMPLIFY OVER OR NEAR ALASKA WHICH ALLOWS
FRESH COLD AIR TO INFILTRATE CANADA AND THE NORTHERN CONUS. BOTTOM
LINE IS ANY WARM UP COULD BE QUICKLY FOLLOWED BY A RETURN TO THE
COLDER THAN NORMAL PATTERN. NO MARCH 2012 PATTERN IS SEEN IN THE
EXTENDED FOR ANYONE HOPING FOR AN EARLY SUMMER AGAIN.
RC
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 14Z...
* FLURRIES WITH SCT LAKE EFFECT SHSN...VIS BRIEFLY DROPPING DOWN IN
THE 2 TO 3 SM RANGE IN THE HEAVIER SHOWERS...ESPECIALLY THIS
MORNING.
* NNW WINDS TO TRANSITION TO N-NE BY LATE MORNING/EARLY AFTERNOON
IZZI/KB
//DISCUSSION...UPDATED 12Z...
EXTENSIVE HIGH END MVFR/LOW END VFR STRATUS DECK BLANKETS THE
REGION WITH SOME POCKETS OF FLURRIES LIKELY TO TO PERSIST THRU
TODAY. LAKE EFFECT FLURRIES AND SCATTERED SNOW SHOWERS WILL
CONTINUE AT LEAST THROUGH THE EARLY AFTERNOON INTO CHGO AREA...AND
POSSIBLY INTO THIS EVENING. SMALL THREAT OF SOME BRIEF VSBY
REDUCTIONS IN -SHSN THIS MORNING...BUT PROBABLY NOT BELOW 3SM WITH
CIGS LIKELY TO BE GENERALLY AT OR ABOVE 1500FT. LAND BREEZE
INFLUENCE TO WIND DIRECTION SHOULD RESULT IN WINDS BEING WEST OF
DUE NORTH WINDS EARLY THIS MORNING AT CHGO AREA TERMINALS WITH
TRANSITION TO MORE NE WINDS EXPECTED LATER THIS MORNING.
IZZI
//ORD AND MDW CONFIDENCE...UPDATED 14Z...
* MEDIUM CONFIDENCE IN SHSN WITH BRIEF PERIODS OF 2 TO 3 SM VIS.
* HIGH CONFIDENCE IN WIND SHIFT TO N-NE...BUT LOW CONFIDENCE IN
EXACT TIMING
* MEDIUM/HIGH CONFIDENCE IN CIGS FORECAST THROUGH THE PERIOD
IZZI/KB
//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...
SATURDAY NIGHT...MVFR CIGS POSSIBLE EARLY.
SUNDAY...VFR.
MONDAY...CHANCE OF LIGHT SNOW IN THE AFTERNOON. MVFR POSSIBLE
LATE.
MONDAY NIGHT INTO TUESDAY...GOOD CHANCE OF SNOW. IFR PROBABLE.
WEDNESDAY...MVFR CIGS POSSIBLE.
THURSDAY...VFR EXPECTED.
IZZI
&&
.MARINE...
222 AM CST
MODERATELY STRONG NORTH WINDS LIKELY TO CONTINUE THROUGH SATURDAY
WITH OCCASIONAL GALE FORCE GUSTS A POSSIBILITY...ESPECIALLY LATER
THIS AFTERNOON INTO THE EVENING...BUT GENERALLY THINK ANY GALES
WILL BE INFREQUENT ENOUGH TO KEEP OUT OF THE FORECAST. WINDS WILL
BEGIN TO DIMINISHING LATER SATURDAY INTO SUNDAY AS RIDGE AXIS
APPROACHES AND THEN MOVES ACROSS THE LAKE SUNDAY NIGHT. ANOTHER
SYSTEM WILL PASS TO THE SOUTHWEST OF THE LAKE EARLY/MIDDLE PART OF
NEXT WEEK WITH WINDS FRESHENING UP A BIT...BUT SYSTEM SHOULD BE
WEAK ENOUGH AND FAR ENOUGH AWAY TO NOT CAUSE ANY MAJOR
WINDS/WAVES.
IZZI
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL 3 AM
SUNDAY.
SMALL CRAFT ADVISORY...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL 9 AM SUNDAY.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
507 AM CST FRI MAR 1 2013
.DISCUSSION...
330 AM CST
FORECAST CONCERNS ARE LAKE EFFECT SNOW SHOWER POTENTIAL THE NEXT FEW
DAYS...COLD TEMPERATURES OVER THE WEEKEND...AND A POSSIBLE SNOW
PRODUCING SYSTEM EARLY NEXT WEEK.
SHORT TERM...TODAY THROUGH SUNDAY NIGHT...
SLIGHTLY COLDER AIR MASS WILL SETTLE OVER THE REGION TODAY ON
CONTINUED NORTHERLY FLOW...WITH A LARGE AREA OF HIGH PRESSURE
BUILDING IN FROM THE NORTH. THIS SHOULD KEEP HIGHS A FEW DEGREES
COOLER THAN YESTERDAY. LAKE EFFECT SET UP IS QUITE MARGINAL
THERMODYNAMICALLY...BUT COMPENSATING SOMEWHAT WILL BE GOOD
CONVERGENCE AND FETCH WITH NORTH-NORTHEAST LOW LEVEL FLOW. THE
CONVERGENCE AND EVEN SOME ENHANCED LIFT IS BEST ALIGNED OVER
ILLINOIS AND PORTION OF NW INDIANA LAKEFRONT THROUGH MID/LATE
MORNING...SO BUMPED UP POPS SOME FROM PREVIOUS FORECAST. COULD SEE
SOME VERY LIGHT ACCUMULATIONS. OUTSIDE OF LAKE EFFECT...THERE MAY BE
SOME FLURRIES INLAND. ALTHOUGH STRATUS CAN CLEAR OUT QUICKER THIS
TIME OF YEAR DUE TO HIGHER SUN ANGLE...THINK THE NAM IS BEING WAY
TOO AGGRESSIVE WITH CLEARING TREND FROM NORTH. USED RAP GUIDANCE FOR
NEAR TERM SKY FORECAST. MOST OF CWA SHOULD SEE OVC THROUGH DAYLIGHT
HOURS.
THE SAME GENERAL IDEA OF DECENT CONVERGENCE BUT VERY MARGINAL
THERMODYNAMICS AND INVERSION HEIGHTS CONTINUES THROUGH SATURDAY WITH
THE LAKE EFFECT. WILL CONTINUE TO CARRY CHANCE POPS...THOUGH THEY
WILL SLIDE INTO NW INDIANA ON SATURDAY AS NORTHERLY FLOW BECOMES
JUST WEST OF DUE NORTH. SKIES SHOULD START TO CLEAR BY DAYBREAK OVER
THE NW CWA...SO TEMPERATURES SHOULD DROP PRETTY WELL THERE GIVEN
THE GOOD RADIATION COOLING...PROBABLY INTO THE MID TEENS.
OUTSIDE OF LAKE EFFECT CONCERNS...THE ONLY FOCUS OVER THE WEEKEND
WAS TEMPERATURES WITH HIGH PRESSURE BUILDING OVERHEAD. FOR HIGHS
ON SATURDAY...SUSPECT THAT THE MARCH SUN WILL GO TO WORK ON THE
SNOW COVER...ESPECIALLY FOR AREAS THAT DIDNT SEE MUCH THIS WEEK.
FOR MARCH 1-15...WITH 850 TEMPS AROUND -10C AS IS PROGGED ON
SATURDAY...MEDIAN HIGH AT ORD IS 34 DEGREES. WENT JUST UNDER THAT
IN NORTHERN CWA/ESPECIALLY IN THE NORTHEAST WHERE SNOW PACK IS
DEEPEST...YIELDING HIGHS AROUND 30. TO THE SOUTH OF I-80...SUSPECT
WE`LL SEE SOME MID TO EVEN UPPER 30S AS SUN EATS AWAY AT MEAGER
SNOW COVER.
THEN SUNDAY NIGHT...THERE IS A STRONG SIGNAL FOR GOOD RADIATIONAL
COOLING...ESPECIALLY ON THE ECMWF...WHICH MAY BE A BIT TOO
AGGRESSIVE WITH ITS ZERO TO SLIGHTLY BELOW ZERO NUMBERS FOR NORTH
CENTRAL IL. BASICALLY CONTINUED IDEA OF PREVIOUS FORECAST WITH
POTENTIAL FOR SINGLE DIGIT LOWS WEST OF FOX RIVER. ON SUNDAY...THE
COLD START MAY KEEP TEMPS IN CHECK SOMEWHAT...BUT MARCH SUN ANGLE
AND LONGER DAYLIGHT HOURS EXPECTED TO COMPENSATE...IN ADDITION TO
SLIGHTLY WARMER TEMPS ALOFT. MEDIAN ORD HIGHS FOR DAYS WITH 850
TEMPS AS PROGGED ON SUNDAY IN -6 TO -8 RANGE IS 38. DIDNT GO THIS
MILD DUE TO COLD START AND SNOW COVER OVER NORTHERN CWA...BUT
BUMPED UP TEMPS A FEW DEGREES FROM PREVIOUS. IF SNOW COVER CAN BE
ELIMINATED ON SATURDAY OVER SOUTH...WOULDNT BE SURPRISED IF SOME
LOCATIONS TAG 40 DEGREES...BUT FOR NOW WENT WITH UPPER 30S IN
CENTRAL IL. INCREASING CLOUD COVER SHOULD RESULT IN LOWS SEVERAL
DEGREES WARMER SUNDAY NIGHT THAN SATURDAY NIGHT.
LONG TERM...MONDAY THROUGH THURSDAY
MAIN FOCUS IS ON VERY ENERGETIC CLIPPER SYSTEM EARLY NEXT WEEK.
THERE HAVE BEEN FAIRLY SIGNIFICANT RUN TO RUN CHANGES WITH THE
TIMING AND TRACK OF THE STRONG UPPER LOW AND SURFACE REFLECTION.
WOULD EXPECT THIS TO CONTINUE UNTIL UPPER WAVE MAKES LANDFALL IN
PACIFIC NORTHWEST SATURDAY NIGHT ALLOWING FOR SAMPLING BY RAOB
NETWORK. AS IT STANDS RIGHT NOW...00Z GUIDANCE HAS SHIFTED BACK
NORTH...WHICH WOULD PUT MOST OF CWA IN LINE FOR A POTENTIALLY
ACCUMULATING SNOW. COULD SEE THE START OF SOME WAA SNOWS AHEAD OF
SYSTEM ON MONDAY...SO BLENDED POPS WERE MAINTAINED.
HOWEVER...BIGGEST CHANGE WAS TO GREATLY INCREASE POPS ABOVE
ALLBLEND MONDAY NIGHT AND TUESDAY IN LINE WITH A SLOWER
PROGRESSION OF THE UPPER LOW AND ATTENDANT SURFACE LOW FAVORED BY
THE 00Z ECMWF...CANADIAN...GEFS AND HPC. GFS APPEARS MUCH TOO FAST
IN CLEARING THE SYSTEM OFF TO THE EAST. FOR NOW...BUMPED UP POPS
TO MID RANGE CHANCE GIVEN UNCERTAINTY.
AS CURRENTLY MODELED...THE UPPER LOW WITH THIS SYSTEM LOOKS QUITE
STRONG...WITH A TIGHT BAROCLINIC ZONE ALONG/AHEAD OF ITS TRACK. THUS
THERE COULD BE A NICE SWATH OF SNOW PUT DOWN SOMEWHERE OVER/NEAR THE
REGION. ON THE NEGATIVE SIDE...TEMPERATURES AS IS USUALLY THE CASE
IN MARCH WOULD BE NEAR FREEZING...SO THE SNOW WOULD HAVE TO COME
DOWN HARD TO ACCUMULATE EFFICIENTLY. LOTS OF TIME TO MONITOR THIS
SYSTEM.
FOR THE REST OF THE EXTENDED AND BEYOND...AFTER A FAIRLY COOL DAY ON
WEDNESDAY BEHIND THE EARLY WEEK SYSTEM...THERE COULD BE BRIEF WARM UP
TO NORMAL TO ABOVE NORMAL AS THE PATTERN TRANSITIONS FROM AN EASTERN
TROUGH/WESTERN RIDGE (POSITIVE PNA) CONFIGURATION TO A WESTERN
TROUGH/EASTERN RIDGE (NEGATIVE PNA) PATTERN. WITH RIDGING FIRST
AMPLIFYING INTO CENTER OF CONUS...WE COULD SEE A FEW DAYS OF
TEMPERATURES AT LEAST BACK INTO THE 40S.
HOWEVER...THE LONG RANGE ENSEMBLES LOOKING BEYOND THIS 7 DAY
FORECAST PERIOD ARE HOLDING ONTO THE IDEA OF MAINTAINING HIGH
LATITUDE BLOCKING/NEGATIVE NAO AND NEGATIVE AO THROUGH MID MARCH.
IN ADDITION...RIDGING MAY AMPLIFY OVER OR NEAR ALASKA WHICH ALLOWS
FRESH COLD AIR TO INFILTRATE CANADA AND THE NORTHERN CONUS. BOTTOM
LINE IS ANY WARM UP COULD BE QUICKLY FOLLOWED BY A RETURN TO THE
COLDER THAN NORMAL PATTERN. NO MARCH 2012 PATTERN IS SEEN IN THE
EXTENDED FOR ANYONE HOPING FOR AN EARLY SUMMER AGAIN.
RC
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 12Z...
* FLURRIES AND POSSIBLY SCT -SHSN...ESPECIALLY THRU EARLY FRI
AFTERNOON
* NNW WINDS TO TRANSITION TO NE FRIDAY MORNING
IZZI
//DISCUSSION...UPDATED 12Z...
EXTENSIVE HIGH END MVFR/LOW END VFR STRATUS DECK BLANKETS THE
REGION WITH SOME POCKETS OF FLURRIES LIKELY TO TO PERSIST THRU
TODAY. LAKE EFFECT FLURRIES AND SCATTERED SNOW SHOWERS WILL
CONTINUE AT LEAST THROUGH THE EARLY AFTERNOON INTO CHGO AREA...AND
POSSIBLY INTO THIS EVENING. SMALL THREAT OF SOME BRIEF VSBY
REDUCTIONS IN -SHSN THIS MORNING...BUT PROBABLY NOT BELOW 3SM WITH
CIGS LIKELY TO BE GENERALLY AT OR ABOVE 1500FT. LAND BREEZE
INFLUENCE TO WIND DIRECTION SHOULD RESULT IN WINDS BEING WEST OF
DUE NORTH WINDS EARLY THIS MORNING AT CHGO AREA TERMINALS WITH
TRANSITION TO MORE NE WINDS EXPECTED LATER THIS MORNING.
IZZI
//ORD AND MDW CONFIDENCE...UPDATED 12Z...
* LOW/MEDIUM CONFIDENCE IN -SHSN POTENTIAL
* HIGH CONFIDENCE IN WIND SHIFT TO NE...BUT LOW CONFIDENCE IN
TIMING
* MEDIUM/HIGH CONFIDENCE IN CIGS FORECAST THROUGH THE PERIOD
IZZI
//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...
SATURDAY NIGHT...MVFR CIGS POSSIBLE EARLY.
SUNDAY...VFR.
MONDAY...CHANCE OF LIGHT SNOW IN THE AFTERNOON. MVFR POSSIBLE
LATE.
MONDAY NIGHT INTO TUESDAY...GOOD CHANCE OF SNOW. IFR PROBABLE.
WEDNESDAY...MVFR CIGS POSSIBLE.
THURSDAY...VFR EXPECTED.
IZZI
&&
.MARINE...
222 AM CST
MODERATELY STRONG NORTH WINDS LIKELY TO CONTINUE THROUGH SATURDAY
WITH OCCASIONAL GALE FORCE GUSTS A POSSIBILITY...ESPECIALLY LATER
THIS AFTERNOON INTO THE EVENING...BUT GENERALLY THINK ANY GALES
WILL BE INFREQUENT ENOUGH TO KEEP OUT OF THE FORECAST. WINDS WILL
BEGIN TO DIMINISHING LATER SATURDAY INTO SUNDAY AS RIDGE AXIS
APPROACHES AND THEN MOVES ACROSS THE LAKE SUNDAY NIGHT. ANOTHER
SYSTEM WILL PASS TO THE SOUTHWEST OF THE LAKE EARLY/MIDDLE PART OF
NEXT WEEK WITH WINDS FRESHENING UP A BIT...BUT SYSTEM SHOULD BE
WEAK ENOUGH AND FAR ENOUGH AWAY TO NOT CAUSE ANY MAJOR
WINDS/WAVES.
IZZI
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL 3 AM
SUNDAY.
SMALL CRAFT ADVISORY...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL 9 AM SUNDAY.
&&
$$
AREA FORECAST DISCUSSION
NWS NORTHERN INDIANA
648 AM EST FRI MAR 1 2013
.AVIATION...
12Z TAFS...SHEARED VORTICITY MAXIMUM ACROSS NORTHERN INDIANA WILL
CONTINUE TO TRACK SOUTHWARD EARLY THIS MORNING. INVERTED SFC
TROUGH EXTENDING FROM SOUTHWEST LOWER MICHIGAN TO NEAR KFWA WILL
CONTINUE TO SAG SOUTH AS THIS VORT MAX PROGRESSES SOUTHWARD...AND
THUS EXPECTING AN END TO PATCHY DRIZZLE/FLURRIES AT KFWA BY THE
13Z-14Z TIMEFRAME. OTHERWISE...BRIEF IMPROVEMENTS TO VFR CIGS
POSSIBLE EARLY THIS MORNING...BUT WOULD SUSPECT ENOUGH LINGERING
MOISTURE MAY GIVE RISE TO DIURNALLY ENHANCED MVFR CIGS AGAIN LATE
MORNING INTO THIS AFTERNOON. WINDS HAVE VEERED MORE NORTHEAST
EARLY THIS MORNING IN ASSOCIATION WITH THE INVERTED TROUGH...AND
SHOULD BACK MORE NORTHERLY BY MID MORNING AS THE TROUGH SHIFTS
SOUTHWARD.
&&
.PREV DISCUSSION... /ISSUED 444 AM EST FRI MAR 1 2013/
SHORT TERM...TODAY THROUGH SATURDAY NIGHT
RELATIVELY QUIET PERIOD IN STORE FOR THE UPCOMING WEEKEND WITH MAIN
SHORT TERM FOCUS ON LINGERING LIGHT PRECIP THIS MORNING...AND
TEMPERATURE TRENDS.
WATER VAPOR IMAGERY/07Z RAP ANALYSIS SUGGEST WEAK UPPER VORT MAX
DROPPING SOUTHWARD ACROSS NORTHERN INDIANA THIS MORNING. HAVE NOTED
SOME UPSWING OVER PAST HOUR ACROSS CENTRAL/SOUTHERN SECTIONS OF
FORECAST AREA OF SOME -FZDZ PER RADAR/SFC OBSERVATIONS BUT FZDZ IS
EXPECTED TO REMAIN LIGHT ENOUGH TO PREVENT SIGNIFICANT IMPACTS THIS
MORNING. WITH AXIS OF WEAK DPVA SHIFTING ACROSS SOUTHERN/CENTRAL
AREAS WILL CONFINE EARLY MORNING FZDZ MENTION TO THESE LOCATIONS
WITH MAINLY DRY CONDITIONS ACROSS THE NORTH WERE LOW LEVEL DRY AIR
ADVECTION HAS BECOME MORE PRONOUNCED IN THE WAKE OF ASSOCIATED WEAK
INVERTED SFC TROUGH FEATURE. MARINE OBS SUGGEST SOME AUGMENTATION TO
SYNOPTIC CONVERGENCE ASSOCIATED WITH THIS TROUGH WITH WEAK LAKE
INDUCED THERMAL TROUGHING. THIS MAY ACT TO PERPETUATE SOME FLURRIES
ACROSS EXTREME NORTHWEST SECTIONS OF THE FORECAST AREA
TODAY...ALTHOUGH INCREASINGLY DRY LOW LEVEL AIR MASS SHOULD LIMIT
FLURRY/LIGHT SNOW SHOWER ACTIVITY. LIMITED DIURNAL MOVEMENT IN
TEMPERATURES EXPECTED AGAIN TODAY WITH RELATIVELY WEAK THERMAL
ADVECTION AND PERSISTENCE OF LOW CLOUD DECK.
FOR TONIGHT INTO SATURDAY...LONGWAVE RIDING ACROSS WESTERN CONUS
WILL BEGIN TO SHIFT EASTWARD AS WEAK UPPER PV ANOMALY ACROSS
NORTHERN PLAINS ADVANCES INTO THE WESTERN GREAT LAKES REGION. UPPER
FORCING/DYNAMICS LOOK TO BE QUITE WEAK WITH THIS SHORT WAVE HOWEVER
AS PV ANOMALY BECOMES AFFECTED BY MID/UPPER LEVEL DEFORMATION FLOW
ACROSS GREAT LAKES REGION. PASSAGE OF THIS FEATURE MAY MARK A SUBTLE
UPSWING IN WEAK LAKE RESPONSE IN THE FORM OF SCT FLURRIES/LIGHT SNOW
SHOWERS SATURDAY/SATURDAY NIGHT. LAKE EFFECT PARAMETERS QUITE MEAGER
HOWEVER WITH VERY DRY MID LEVEL AIR IN PLACE...AND MARGINAL LAKE/850
HPA DELTA TEMPS. DESPITE SOME WEAK REINFORCING LOW LEVEL CAA WITH
AFOREMENTIONED NORTHERN PLAINS SHORT WAVE SATURDAY...HIGH TEMPS
SHOULD BE SIMILAR TO THAT OF FRIDAY WITH THE POSSIBILITY OF A BIT
MORE INSOLATION OFFSETTING SLIGHTLY COOLER LOW LEVEL THERMAL
PROFILES.
&&
LONG TERM...
SUNDAY THROUGH THURSDAY...THE MAIN CHALLENGE THIS PERIOD IS THE
TIMING AND TRACK OF A SHORT WAVE THAT WILL TOP THE UPSTREAM RIDGE
AND MOVE INTO THE MIDWEST NEXT WEEK. THE ECMWF APPEARS TO HAVE
INITIALIZED THIS SYSTEM REASONABLY WELL AND HAS ALSO SHOWN SOME RUN
TO RUN CONSISTENCY. FOR THIS PACKAGE...BLENDED SEVERAL MODELS
INCLUDING THE ECMWF OPERATIONAL RUN...EC ENSEMBLE MEAN...AND GFS
OPERATIONAL RUN WITH ENSEMBLE MEMBERS. GIVEN THE HIGH LATITUDE
STRONG POSITIVE ANOMALY...CONCERN THAT THESE MODELS MAY BE TOO FAST
WITH THIS SYSTEM. THE ECMWF HAS TRENDED SLIGHTLY SLOWER WITH THIS
SYSTEM WITH AN ARRIVAL TIME OF TUESDAY/TUESDAY NIGHT. HAVE TRENDED
THE SNOW CHANCES HIGHER THESE PERIODS...BUT KEPT IN CHANCE CATEGORY
DUE TO A LARGE GFS ENSEMBLE SPREAD AND LARGE NORMALIZED STANDARD
DEVIATIONS AMONG ECMWF ENSEMBLE MEMBERS. A WEAK LAKE RESPONSE IS
EXPECTED AFTER THIS SYSTEM PASSES...BUT DELTA T VALUES SHOULD REMAIN
LESS THAN 10. OTHERWISE...KEPT TEMPERATURES COLD THROUGH WEDNESDAY.
TEMPS SHOULD RISE ABOVE NORMAL THURSDAY AS AN UPPER LEVEL RIDGE
BUILDS OVER THE REGION. GFS MEAN ENSEMBLE MEX MOS TEMPS APPEAR ON
TRACK.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 5 AM EST SUNDAY FOR LMZ043-046.
&&
$$
SHORT TERM...MARSILI
LONG TERM...SKIPPER
AVIATION...MARSILI
AREA FORECAST DISCUSSION
NWS DULUTH MN
610 AM CST FRI MAR 1 2013
.UPDATE...HAVE ADDED A MENTION OF FLURRIES TO THE HEAD OF LAKE
SUPERIOR INCLUDING THE TWIN PORTS FOR EARLY THIS MORNING. REST OF
THE FORECAST UNCHANGED.
&&
.PREV DISCUSSION... /ISSUED 544 AM CST FRI MAR 1 2013/
AVIATION...12Z TAFS
MVFR CEILINGS REMAINED FROM ABOUT KTWM INTO THE KBRD AREA...AND
COVERED ALL AREAS TO THE SOUTHEAST INCLUDING NORTHWEST WISCONSIN.
EAST NORTHEAST WINDS WILL CONTINUE TO GENERATE CLOUDS
TODAY AROUND LAKE SUPERIOR...ALTHOUGH WE DO THINK THEY WILL DISSIPATE
SOME FROM THE NORTH. DRIER AIR IS FORECAST TO MOVE OVER LAKE
SUPERIOR...AND THAT SHOULD HELP DISSIPATE SOME OF THE
CLOUDS...PARTICULARLY OVER KDLH. THE CEILINGS AT KBRD SHOULD ALSO
DIMINISH THROUGH THE DAY. THE RAP DOES SUGGEST MORE MVFR CEILINGS
MAY DEVELOP THIS AFTERNOON...SO WE INCLUDED A TEMPO GROUP AT
KBRD/KHIB. SOME FLURRIES WILL ALSO OCCUR UNDER SOME OF THESE
CLOUDS.
PREV DISCUSSION... /ISSUED 244 AM CST FRI MAR 1 2013/
SHORT TERM...LITTLE CHANGE TO THE PRESSURE PATTERN FROM 24 HOURS
AGO. THE TROF REMAINS STUCK NEAR THE RED RIVER VALLEY WITH THE
RIDGE AXIS TO THE W AND THE LARGE SFC LOW NOW OFF THE E
COAST...BUT CIRCULATION OVER THE FA REMAINS THE SAME. THE
DIFFERENCE IS CLOUD COVER WITH CI AND A FEW MID CLOUDS OVER THE MN
FA AND LOW CLOUDS OVER NW WI TO NEAR THE TWIN PORTS. THE SFC TROF
WILL EVENTUALLY BREAK DOWN TODAY AS THE SFC RIDGE MOVES E AND OVER
THE FA BY 00Z SATURDAY. WILL TAKE AWHILE FOR THE CLOUDS TO ERODE
AS THE RIDGE SLOWLY MOVES OVERHEAD. EVEN WITH THE NE FLOW
CONTINUING OVER LAKE SUPERIOR...AIR MASS IS TOO DRY FOR ANY LES TO
FORM AND HAVE REMOVED THE MENTION OF FLURRIES.
THE SFC RIDGE AXIS REMAINS NEARLY STATIONARY OVER THE FA THROUGH
SATURDAY. WITH A NLY FLOW ALOFT AND 850MB TEMPS AROUND -12C...MIN
TEMPS TONIGHT WILL DROP BELOW ZERO OVER THE NORTHERN HALF OF THE FA.
PLENTY OF SUN ON SATURDAY WILL NOT BE ENOUGH TO COUNTERACT THE COLD
AIR ALOFT AND MAX TEMPS WILL BE IN THE 20S WITH SOME SPOTS REACHING
30F.
LONG TERM...FRIDAY NIGHT THROUGH THURSDAY.
SEVERAL CONCERNS EXIST THROUGH THE PERIOD...NAMELY CHANCES FOR LAKE
EFFECT SNOW AND THE TRACK OF A STRONGER LOW PRESSURE SYSTEM THAT
COULD IMPACT THE NORTHLAND AS EARLY AS SUNDAY NIGHT...BUT MORE SO
MONDAY INTO MONDAY NIGHT.
THE MODELS ARE NOT IN REAL GOOD AGREEMENT THROUGH THE EXTENDED
PERIOD...WITH BOTH RUN TO RUN AND MODEL TO MODEL VARIABILITY.
EARLY IN THE PERIOD AN UPPER LEVEL TROUGH WILL EXTEND OVER LAKE
SUPERIOR INTO MICHIGAN...WITH THE STRONGER SHORTWAVE OVER THE
NORTHWEST CONUS/BC AREA. LOW LEVEL FLOW WILL BECOME SOUTHEAST
SATURDAY NIGHT...AND AN AREA OF LOW LEVEL WAA WILL APPROACH THE CWA
FROM THE WEST. THERE WILL BE A CHANCE FOR LIGHT SNOW WITH THE WAA
SATURDAY NIGHT OVER MUCH OF THE CWA...BUT AMOUNTS WILL BE LIGHT. WE
ADDED/INCREASED POPS ALONG THE NORTH SHORE SATURDAY NIGHT INTO
SUNDAY DUE TO A LONG FETCH WITH MARGINAL DELTA-T/S. THE AIR MASS DOES
NOT LOOK AS DRY AS EARLIER RUNS...AND GIVEN LONG FETCH AND SOME
SYNOPTIC LIFT...SOME LES CAN`T BE RULED OUT.
EMPHASIS SHIFTS TO THE APPROACHING STORM FOR SUNDAY NIGHT INTO
TUESDAY. THERE HAS BEEN A GENERAL SHIFT NORTH WITH THE EXPECTED
TRACK OF THE SYSTEM. THE GEM/NAM ARE QUITE A BIT FARTHER
NORTH...WITH THE GFS NOW THE MOST SOUTHERLY. HOWEVER...SEVERAL OF
THE GFS ENSEMBLE MEMBERS DO SHOW THE LOW/PRECIP QUITE A BIT FURTHER
NORTH THAN THE OPERATIONAL RUN. PICKING ONE PARTICULAR SOLUTION AT
THIS TIME IS JUST TOO DIFFICULT. WE DID INCREASE POPS SUNDAY NIGHT
INTO MONDAY...MAINLY ACROSS OUR SOUTHERN CWA.
THERE WILL BE A CHANCE FOR SOME LAKE EFFECT SNOW FROM ABOUT SILVER
BAY TO THE TWIN PORTS...AND ALONG THE SOUTH SHORE SUNDAY NIGHT INTO
TUESDAY. 850MB TEMPS WILL REMAIN FROM -10C TO -12C...WITH A PRETTY
GOOD FETCH. MOISTURE WILL BE AN ISSUE DEPENDING ON THE TRACK OF THE
LOW.
HOPEFULLY WE`LL SEE BETTER AGREEMENT WITH THE MODEL RUNS TODAY AND
INTO THE WEEKEND...AND WE CAN ADJUST THE FORECAST FROM THERE.
&&
.POINT TEMPS/POPS...
DLH 25 2 28 13 / 10 0 0 30
INL 24 -9 30 10 / 0 0 0 30
BRD 29 4 29 16 / 0 0 0 20
HYR 28 -1 29 0 / 0 0 0 10
ASX 26 6 28 5 / 0 0 0 10
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
SHORT TERM...GSF
AREA FORECAST DISCUSSION
NWS DULUTH MN
544 AM CST FRI MAR 1 2013
.AVIATION...12Z TAFS
MVFR CEILINGS REMAINED FROM ABOUT KTWM INTO THE KBRD AREA...AND
COVERED ALL AREAS TO THE SOUTHEAST INCLUDING NORTHWEST WISCONSIN.
EAST NORTHEAST WINDS WILL CONTINUE TO GENERATE CLOUDS
TODAY AROUND LAKE SUPERIOR...ALTHOUGH WE DO THINK THEY WILL DISSIPATE
SOME FROM THE NORTH. DRIER AIR IS FORECAST TO MOVE OVER LAKE
SUPERIOR...AND THAT SHOULD HELP DISSIPATE SOME OF THE
CLOUDS...PARTICULARLY OVER KDLH. THE CEILINGS AT KBRD SHOULD ALSO
DIMINISH THROUGH THE DAY. THE RAP DOES SUGGEST MORE MVFR CEILINGS
MAY DEVELOP THIS AFTERNOON...SO WE INCLUDED A TEMPO GROUP AT
KBRD/KHIB. SOME FLURRIES WILL ALSO OCCUR UNDER SOME OF THESE
CLOUDS.
&&
.PREV DISCUSSION... /ISSUED 244 AM CST FRI MAR 1 2013/
SHORT TERM...LITTLE CHANGE TO THE PRESSURE PATTERN FROM 24 HOURS
AGO. THE TROF REMAINS STUCK NEAR THE RED RIVER VALLEY WITH THE
RIDGE AXIS TO THE W AND THE LARGE SFC LOW NOW OFF THE E
COAST...BUT CIRCULATION OVER THE FA REMAINS THE SAME. THE
DIFFERENCE IS CLOUD COVER WITH CI AND A FEW MID CLOUDS OVER THE MN
FA AND LOW CLOUDS OVER NW WI TO NEAR THE TWIN PORTS. THE SFC TROF
WILL EVENTUALLY BREAK DOWN TODAY AS THE SFC RIDGE MOVES E AND OVER
THE FA BY 00Z SATURDAY. WILL TAKE AWHILE FOR THE CLOUDS TO ERODE
AS THE RIDGE SLOWLY MOVES OVERHEAD. EVEN WITH THE NE FLOW
CONTINUING OVER LAKE SUPERIOR...AIR MASS IS TOO DRY FOR ANY LES TO
FORM AND HAVE REMOVED THE MENTION OF FLURRIES.
THE SFC RIDGE AXIS REMAINS NEARLY STATIONARY OVER THE FA THROUGH
SATURDAY. WITH A NLY FLOW ALOFT AND 850MB TEMPS AROUND -12C...MIN
TEMPS TONIGHT WILL DROP BELOW ZERO OVER THE NORTHERN HALF OF THE FA.
PLENTY OF SUN ON SATURDAY WILL NOT BE ENOUGH TO COUNTERACT THE COLD
AIR ALOFT AND MAX TEMPS WILL BE IN THE 20S WITH SOME SPOTS REACHING
30F.
LONG TERM...FRIDAY NIGHT THROUGH THURSDAY.
SEVERAL CONCERNS EXIST THROUGH THE PERIOD...NAMELY CHANCES FOR LAKE
EFFECT SNOW AND THE TRACK OF A STRONGER LOW PRESSURE SYSTEM THAT
COULD IMPACT THE NORTHLAND AS EARLY AS SUNDAY NIGHT...BUT MORE SO
MONDAY INTO MONDAY NIGHT.
THE MODELS ARE NOT IN REAL GOOD AGREEMENT THROUGH THE EXTENDED
PERIOD...WITH BOTH RUN TO RUN AND MODEL TO MODEL VARIABILITY.
EARLY IN THE PERIOD AN UPPER LEVEL TROUGH WILL EXTEND OVER LAKE
SUPERIOR INTO MICHIGAN...WITH THE STRONGER SHORTWAVE OVER THE
NORTHWEST CONUS/BC AREA. LOW LEVEL FLOW WILL BECOME SOUTHEAST
SATURDAY NIGHT...AND AN AREA OF LOW LEVEL WAA WILL APPROACH THE CWA
FROM THE WEST. THERE WILL BE A CHANCE FOR LIGHT SNOW WITH THE WAA
SATURDAY NIGHT OVER MUCH OF THE CWA...BUT AMOUNTS WILL BE LIGHT. WE
ADDED/INCREASED POPS ALONG THE NORTH SHORE SATURDAY NIGHT INTO
SUNDAY DUE TO A LONG FETCH WITH MARGINAL DELTA-T/S. THE AIR MASS DOES
NOT LOOK AS DRY AS EARLIER RUNS...AND GIVEN LONG FETCH AND SOME
SYNOPTIC LIFT...SOME LES CAN`T BE RULED OUT.
EMPHASIS SHIFTS TO THE APPROACHING STORM FOR SUNDAY NIGHT INTO
TUESDAY. THERE HAS BEEN A GENERAL SHIFT NORTH WITH THE EXPECTED
TRACK OF THE SYSTEM. THE GEM/NAM ARE QUITE A BIT FARTHER
NORTH...WITH THE GFS NOW THE MOST SOUTHERLY. HOWEVER...SEVERAL OF
THE GFS ENSEMBLE MEMBERS DO SHOW THE LOW/PRECIP QUITE A BIT FURTHER
NORTH THAN THE OPERATIONAL RUN. PICKING ONE PARTICULAR SOLUTION AT
THIS TIME IS JUST TOO DIFFICULT. WE DID INCREASE POPS SUNDAY NIGHT
INTO MONDAY...MAINLY ACROSS OUR SOUTHERN CWA.
THERE WILL BE A CHANCE FOR SOME LAKE EFFECT SNOW FROM ABOUT SILVER
BAY TO THE TWIN PORTS...AND ALONG THE SOUTH SHORE SUNDAY NIGHT INTO
TUESDAY. 850MB TEMPS WILL REMAIN FROM -10C TO -12C...WITH A PRETTY
GOOD FETCH. MOISTURE WILL BE AN ISSUE DEPENDING ON THE TRACK OF THE
LOW.
HOPEFULLY WE`LL SEE BETTER AGREEMENT WITH THE MODEL RUNS TODAY AND
INTO THE WEEKEND...AND WE CAN ADJUST THE FORECAST FROM THERE.
&&
.POINT TEMPS/POPS...
DLH 25 2 28 13 / 0 0 0 30
INL 24 -9 30 10 / 0 0 0 30
BRD 29 4 29 16 / 0 0 0 20
HYR 28 -1 29 0 / 0 0 0 10
ASX 26 6 28 5 / 0 0 0 10
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
SHORT TERM...GSF
LONG TERM....MELDE
AVIATION...MELDE
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
537 AM CST FRI MAR 1 2013
.SHORT TERM...TODAY THROUGH SUNDAY NIGHT
308 AM CST FRI MAR 1 2013
POTENTIAL FOR ACCUMULATING SNOW SUNDAY NIGHT AND HEADING INTO THE
LONG TERM PERIOD.
CURRENTLY AS OF 09Z...WATER VAPOR LOOP AND RAP 500MB HEIGHT ANALYSIS
SHOWED RIDGING OVER THE WESTERN U.S. INTO ALBERTA AND GENERAL BROAD
TROUGHING OVER THE EAST HALF OF THE U.S.. THE FORECAST AREA SITS IN
A NON-DESCRIPT FLOW WITHIN THIS BROAD TROUGH...DUE TO THE MAIN JET
FLOW CONFINED OVER THE WESTERN DAKOTAS...AND AN UPPER LOW STUCK OVER
NEW ENGLAND. THIS NON-DESCRIPT FLOW HAS RESULTED IN THE VERY SLOW
SURFACE PATTERN PROGRESSION...WITH THE AREA STILL UNDER CYCLONIC
FLOW AROUND LOW PRESSURE IN NEW ENGLAND. A TROUGH EXTENDING WEST
FROM THE LOW EXTENDS WEST NEAR I-80 TO DES MOINES...THEN TO THE
NORTHWEST TO FARGO. SLOWLY DRIER AIR IS ADVECTING SOUTHWARD INTO THE
CYCLONIC CIRCULATION FROM HIGH PRESSURE OVER HUDSON BAY...RESULTING
IN CLEARING OVER NORTHERN LAKE SUPERIOR INTO THE NORTHERN 2/3 OF
MINNESOTA. HOWEVER...THE 00Z MPX AND GRB SOUNDINGS STILL SHOW A 50MB
SATURATED LAYER STUCK AROUND A COLD FRONTAL INVERSION SITTING AT
825MB. THUS...STRATUS STILL COVERS THE AREA. THIS STRATUS COMBINED
WITH A 5-10 KT NORTHEAST WIND HAS KEPT TEMPERATURES MAINLY IN THE
20S...DESPITE 850MB TEMPS AROUND -11C OR 1 STANDARD DEVIATION BELOW
NORMAL PER 00Z RAOBS.
SHORT TERM HIGHLIGHTS / CONCERNS:
1. WHEN WILL IT CLEAR
THIS IS A TWO PART ISSUE. FIRST AND MORE IMPORTANTLY IS THE GENERAL
STRATUS DECK IN PLACE. 01.00Z NAM WAS SURPRISINGLY TOO AGGRESSIVE
WITH CLEARING...SUGGESTING BASED ON 850MB AND 900MB RH FIELDS THAT
LOCATIONS NORTH OF I-90 WOULD BE CLEAR RIGHT NOW. LATEST RAP 850MB
AND 900MB RH GUIDANCE SEEMS TO HAVE A BETTER HANDLE ON THE LOW
CLOUDS...GRADUALLY CLEARING LOCATIONS NORTH OF I-90 NORTH TO SOUTH
THROUGH 21Z. A COMBINATION OF DAYTIME MIXING AND A STRONGER SURGE OF
DRY AIR FROM NORTHERN ONTARIO APPEARS TO BE AIDING IN THIS CLEARING.
SOUTH OF I-90...THE LOW CLOUDS MAY NOT DISSIPATE UNTIL SOMETIME
DURING THE EVENING. THE SECOND PART OF THE CLEARING ISSUE IS IN THE
UPPER LEVELS WHERE SCT-BKN CIRROSTRATUS EXISTS OVER THE AREA. THE
NON-DESCRIPT UPPER LEVEL FLOW WOULD SUGGEST CLEARING OF THE CIRRUS
WILL BE PROBLEMATIC. NAM/RAP 500-400MB RH FIELD CONFIRM THIS AS WELL
WITH MUCH OF THE AREA DOMINATED BY SCT-BKN CIRROSTRATUS THROUGH THE
DAY TODAY...ESPECIALLY OVER THE WESTERN HALF. IT LOOKS LIKE WE
FINALLY CAN CLEAR THESE HIGH CLOUDS OUT TONIGHT INTO SATURDAY
MORNING AS THE UPPER RIDGE OVER THE WESTERN U.S. BEGINS PROGRESSING
EAST.
2. TEMPERATURES TODAY THROUGH SATURDAY NIGHT
THE STRONGER NOW EARLY MARCH SUN CAN DEFINITELY WARM TEMPERATURES
UP...EVEN UNDER AN ENVIRONMENT OF COLD 850MB TEMPS...LIKE THOSE
TODAY AROUND -11C. HOWEVER...WITH ONLY PARTIAL CLEARING OVERALL
NORTH OF I-90...IT LOOKS TOUGH TO GET TEMPERATURES TO OR ABOVE
FREEZING. NAM 2 METER AND MET GUIDANCE LOOKS A BIT TOO OPTIMISTIC...
GIVEN THE FACT THAT IT HAS CLEARING MUCH EARLIER THAN WHAT WILL
OCCUR. HAVE LEANED MORE TOWARDS MAV/ECMWF/GEM GUIDANCE AS A RESULT.
RELATIVELY COOL CONDITIONS TODAY COMBINED WITH CLEARING TONIGHT AND
WINDS CALMING WITH HIGH PRESSURE BUILDING IN SETS THE STAGE FOR A
DECENT RADIATIONAL COOLING NIGHT. THUS...STAYED TOWARD THE COOL END
OF GUIDANCE. MUCH MORE SUN ON SATURDAY WITH SIMILAR 850MB TEMPS WILL
YIELD JUST A SLIGHTLY WARMER DAY. THE SURFACE HIGH PRESSURE RIDGE IS
PROGGED TO REMAIN NEARBY SATURDAY NIGHT...WHICH AGAIN PUTS A GOOD
RADIATIONAL COOLING NIGHT IN FOCUS. HOWEVER...MID AND HIGH CLOUDS
LOOK TO INCREASE COMING THROUGH THE UPPER RIDGE BUILDING TOWARDS US.
THUS...WE SHOULD NOT GET AS COOL AS TONIGHT. STILL...TIMING OF THE
CLOUDS IS EVERYTHING AND TYPICAL COLD SPOTS IN WISCONSIN COULD STILL
END UP PLUMMETING. THUS...FOR THE TYPICAL COLD SPOTS LEANED MORE
TOWARDS THE COLDER SIDE OF GUIDANCE FOR THEM.
3. POTENTIAL FOR WARM ADVECTION PRECIPITATION SUNDAY/SUNDAY NIGHT
MODELS ARE PROGGING THAT A POTENT UPPER TROUGH...CURRENTLY PRESENT
NEAR 45 N / 150W WELL SOUTH OF THE GULF OF ALASKA...WILL CRASH
THROUGH THE UPPER RIDGING BUILDING TOWARDS THE FORECAST AREA DURING
THE WEEKEND. BY 12Z SUNDAY...GOOD MODEL AGREEMENT EXISTS THAT THIS
POTENT UPPER TROUGH...PERHAPS IN THE FORM OF A CLOSED LOW...SHOULD
BE OVER WASHINGTON STATE. THERE STILL REMAINS SOME DISAGREEMENT ON
THE TRACK OF THE POTENT UPPER TROUGH AFTERWARDS...BUT THERE DOES
APPEAR TO BE A CONVERGING SOLUTION. BY 12Z MONDAY...THE TROUGH
SHOULD EXIST SOMEWHERE BETWEEN ENTERING WESTERN SOUTH DAKOTA
/SLOWER 01.00Z ECMWF/ TO SOUTHEAST SOUTH DAKOTA /FASTER 01.00Z NAM/.
THE SPEED FACTOR APPEARS TO BE RELATED TO HOW POTENT A SHORTWAVE IS
DROPPING THROUGH MICHIGAN ON SUNDAY...THE MORE POTENT THE SLOWER THE
UPPER TROUGH COMING ACROSS THE NORTHERN ROCKIES WILL BE. THIS
FORECAST IS GOING TO TAKE A CONSENSUS APPROACH TO THE 01.00Z
GUIDANCE...GIVEN THE CONVERGING TREND BUT AT THE SAME TIME ALLOWS
FOR A LITTLE CONTINUITY.
DETAILS...AS THE POTENT TROUGH DIGS INTO THE NORTHERN ROCKIES ON
SUNDAY...LOW PRESSURE DEEPENS DOWNSTREAM OVER SOUTH DAKOTA AND
NEBRASKA. IN TURN...WARM ADVECTION INTENSIFIES...DEVELOPING A MASS
OF MID CLOUDS FROM THE DAKOTAS INTO THE FORECAST AREA. THE 00Z
GFS/UKMET/CANADIAN ALL DEVELOP SOME LIGHT PRECIP WEST OF THE
MISSISSIPPI RIVER BETWEEN 18-00Z...BUT UNSURE IF THIS IS GOING TO
REACH THE GROUND AS REFLECTED BY THE 00Z ECMWF. INCLUDED JUST A 20
PERCENT CHANCE OVER SOUTHEAST MN FOR NOW. CHANCES INCREASE
EVERYWHERE SUNDAY NIGHT...ESPECIALLY WEST OF THE MISSISSIPPI
RIVER...ASSOCIATED WITH THE TROUGH PUSHING EAST AND MORE IMPORTANTLY
THE LOW TO MID-LEVEL FRONTOGENESIS ZONE STRENGTHENING. INCREASED
CHANCES TOWARD 60 LATE IN THE NIGHT WEST OF HWY 52.
ANOTHER CONCERN TO WATCH IS A POTENTIAL WARM LAYER ACCOMPANYING THIS
SYSTEM. THE FASTEST 01.00Z NAM WOULD SUGGEST THAT THE PRECIPITATION
SUNDAY AFTERNOON OR EVENING WOULD START AS SLEET SAY IN THE AUSTIN
AREA. HOWEVER...SINCE A COMPROMISE APPROACH WAS FOLLOWED...ANY MIXED
PRECIPITATION TYPE TRANSITION ZONE SHOULD STAY OFF TO THE WEST.
.LONG TERM...MONDAY THROUGH THURSDAY NIGHT
308 AM CST FRI MAR 1 2013
MAIN CONCERN/FOCUS OF THE LONG TERM PERIOD REMAINS ON THE POTENT
UPPER TROUGH IN SOUTH DAKOTA EARLY MONDAY. THE 01.00Z
ECMWF/UKMET/CANADIAN AND GFS ENSEMBLES ARE ALL IN GOOD AGREEMENT
THAT THIS TROUGH WILL CLOSE OFF AND BE IN/NEAR WESTERN IOWA BY 12Z
TUESDAY. NOTE THAT THE 01.00Z GFS ALSO CLOSES IT OFF...BUT IS MUCH
MORE PROGRESSIVE...DOWN IN SOUTHERN MISSOURI AT 12Z TUESDAY. GIVEN
THE PREDOMINANCE OF SLOWER SOLUTIONS...DISCOUNTED THE GFS. THESE
SLOWER SOLUTIONS MEAN THAT A LOW TO MID-LEVEL FRONTOGENESIS BAND
WILL GET STUCK. WHEREVER THIS OCCURS THERE COULD END UP BEING SOME
DECENT SNOW ACCUMULATIONS. RIGHT NOW IT APPEARS THE BAND WOULD SET
UP FROM NORTH DAKOTA INTO SOUTHEAST MN AND INTO EASTERN IOWA. RAISED
PRECIPITATION CHANCES IN THIS AREA 20 PERCENT FROM THE PREVIOUS
FORECAST...AND MAY NEED TO BE RAISED MORE IF TRENDS CONTINUE.
A LONGWAVE TROUGH IS FORECAST TO TRY TO ENTER THE WEST COAST TUESDAY
NIGHT...WHICH MODELS HAVE SHOWN FOR AWHILE. THIS TROUGH WILL HELP
BUILD AND PUSH RIDGING EASTWARD...CAUSING THE UPPER LOW OVER WESTERN
IOWA TO SHIFT SOUTHEAST...AND PUSH THE LOW TO MID-LEVEL
FRONTOGENESIS CIRCULATION EASTWARD. THUS...THE SNOW MAY END UP
OVERSPREADING MUCH OF THE AREA ON TUESDAY AND ADDED 20-40 PERCENT
CHANCES AS A RESULT. EVEN ADDED A 20 PERCENT CHANCE OVER THE
SOUTHEAST 1/3 TUESDAY NIGHT.
WHEN ALL IS SAID AND DONE FROM THE SUNDAY NIGHT THROUGH TUESDAY
PERIOD...WE COULD BE LOOKING AT EITHER A LONG DURATION ADVISORY
EVENT OR EVEN WARNING IF THE 01.00Z CANADIAN ENDS UP RIGHT.
DEFINITELY NEED MODELS TO COME TO BETTER AGREEMENT AND MORE
DETAILS WORKED OUT BEFORE SPECULATING ON SNOWFALL AMOUNTS. 01.06Z
NAM CONTINUES TO SHOW AN AGGRESSIVE QPF SCENARIO SIMILAR TO THE
CANADIAN...ALONG WITH SPREADING PRECIPITATION FARTHER EAST. QUICK
LOOK AT THE 01.00Z ECMWF ENSEMBLE MEAN ALSO APPEARS TO BE IN-LINE
WITH THE NAM/CANADIAN IN TERMS OF 500MB HEIGHT AND MSLP. AS
MENTIONED...PLENTY OF DETAILS TO WORK OUT.
QUIET WEATHER ROUNDS OUT THE REST OF THE WEEK WITH MODELS IN GOOD
AGREEMENT SHIFTING THE UPPER RIDGE INTO THE FORECAST AREA. THIS
SHOULD BRING TEMPERATURES BACK UP TO NEAR OR POSSIBLY EVEN ABOVE
NORMAL BY THURSDAY. IF THE 01.00Z GFS IS CORRECT...WE COULD EVEN BE
LOOKING AT A RAIN/SNOW MIX THURSDAY NIGHT AS IT EJECTS OUT A
SHORTWAVE FROM THE WESTERN TROUGH THROUGH/NEARBY THE FORECAST AREA.
&&
.AVIATION...TODAY AND TONIGHT
537 AM CST FRI MAR 1 2013
STRATUS WILL PRODUCE MAINLY MVFR CONDITIONS AT THE TAF SITES INTO
EARLY THIS AFTERNOON WITH CLOUDS BASES AROUND 3000 FT AT KLSE AND
2500 FT AT KRST. WEAK HIGH PRESSURE IS EXPECTED TO GRADUALLY BUILD
IN THIS AFTERNOON WITH THE STRATUS BECOMING BROKEN TO SCATTERED.
WILL HAVE TO KEEP A CLOSE WATCH ON CLOUD TRENDS TODAY WITH
GUIDANCE NOT HANDLING THIS STRATUS LAYER VERY WELL THIS MORNING.
VFR CONDITIONS ARE EXPECTED THIS EVENING INTO THE OVERNIGHT HOURS
WITH SKIES BECOMING MOSTLY CLEAR. PLAN ON NORTH/NORTHEAST WINDS AT
5 TO 10 KTS.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
308 AM CST FRI MAR 1 2013
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...AJ
LONG TERM...AJ
AVIATION...WETENKAMP
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
223 PM CST FRI MAR 1 2013
.DISCUSSION...
919 AM CST
UPDATED THE GRIDS FOR THIS MORNING...MAINLY TO ACCOUNT FOR ONGOING
LAKE EFFECT SNOW SHOWERS.
LATEST RADAR IMAGERY DEPICTING SOME LIGHT RETURNS ACROSS ALL OF
NORTHERN ILLINOIS WITH AN ISOLATED AREA OF FAIRLY DECENT
RETURNS...PRIMARILY ACROSS SOUTHEAST COOK COUNTY AND NORTHWEST
LAKE COUNTY IN INDIANA. UNDER THE LIGHTER RETURNS LIGHT SNOW
CONTINUES WITH VIS STAYING CONFINED TO ONLY THE 3-6 MILE
RANGE...WITH VIS LIKELY AT OR UNDER 1 MILE UNDER THE STRONGER
RETURNS. THESE SNOW SHOWERS ARE IN RESPONSE TO PERSISTENT
NORTH/NORTHEAST FLOW OFF OF A MODERATELY UNSTABLE LAKE...AS WELL
AS WEAK LARGE SCALE LIFT. LATEST SURFACE ANALYSIS INDICATING A
SURFACE TROUGH SITUATED ACROSS THE SOUTHERN HALF OF THE
LAKE...EXTENDING BACK NORTHWEST FROM A WEAK SURFACE LOW OVER
IN/KY. THIS HAS RESULTED IN AN AREA OF BETTER CONVERGENCE THIS
MORNING...WHICH HAS THEN PROVIDED THIS ISOLATED AREA OF STRONGER
SNOW SHOWERS. LATEST SHORT TERM GUIDANCE IS INDICATING THIS TROUGH
TO SLOWLY EXIT/DAMPEN WITH ALL SURFACE WINDS BECOMING MORE
NORTHERLY...AND LOSS OF BETTER CONVERGENCE. SO DO EXPECT THIS
ISOLATED AREA OF STRONGER SNOW SHOWERS TO PERSIST OVER THE NEXT
COUPLE OF HOURS...ONCE AGAIN PRIMARILY AFFECTING ONLY SOUTHEAST
COOK AND NORTHWEST LAKE COUNTY IN INDIANA. UNDER THESE STRONGER
RETURNS IT WOULD NOT BE OUT OF THE QUESTION FOR SOME ADDITIONAL
ACCUMULATIONS...WITH 1 TO 3 INCHES NOT OF THE REALM OF
POSSIBILITY THROUGH MID DAY. LIGHT SNOW SHOWERS ARE THEN EXPECTED
TO CONTINUE INTO THE AFTERNOON...BUT WITH ONLY LIGHT ACCUMULATIONS
ANTICIPATED.
RODRIGUEZ
//PREV DISCUSSION...
330 AM CST
FORECAST CONCERNS ARE LAKE EFFECT SNOW SHOWER POTENTIAL THE NEXT FEW
DAYS...COLD TEMPERATURES OVER THE WEEKEND...AND A POSSIBLE SNOW
PRODUCING SYSTEM EARLY NEXT WEEK.
SHORT TERM...TODAY THROUGH SUNDAY NIGHT...
SLIGHTLY COLDER AIR MASS WILL SETTLE OVER THE REGION TODAY ON
CONTINUED NORTHERLY FLOW...WITH A LARGE AREA OF HIGH PRESSURE
BUILDING IN FROM THE NORTH. THIS SHOULD KEEP HIGHS A FEW DEGREES
COOLER THAN YESTERDAY. LAKE EFFECT SET UP IS QUITE MARGINAL
THERMODYNAMICALLY...BUT COMPENSATING SOMEWHAT WILL BE GOOD
CONVERGENCE AND FETCH WITH NORTH-NORTHEAST LOW LEVEL FLOW. THE
CONVERGENCE AND EVEN SOME ENHANCED LIFT IS BEST ALIGNED OVER
ILLINOIS AND PORTION OF NW INDIANA LAKEFRONT THROUGH MID/LATE
MORNING...SO BUMPED UP POPS SOME FROM PREVIOUS FORECAST. COULD SEE
SOME VERY LIGHT ACCUMULATIONS. OUTSIDE OF LAKE EFFECT...THERE MAY BE
SOME FLURRIES INLAND. ALTHOUGH STRATUS CAN CLEAR OUT QUICKER THIS
TIME OF YEAR DUE TO HIGHER SUN ANGLE...THINK THE NAM IS BEING WAY
TOO AGGRESSIVE WITH CLEARING TREND FROM NORTH. USED RAP GUIDANCE FOR
NEAR TERM SKY FORECAST. MOST OF CWA SHOULD SEE OVC THROUGH DAYLIGHT
HOURS.
THE SAME GENERAL IDEA OF DECENT CONVERGENCE BUT VERY MARGINAL
THERMODYNAMICS AND INVERSION HEIGHTS CONTINUES THROUGH SATURDAY WITH
THE LAKE EFFECT. WILL CONTINUE TO CARRY CHANCE POPS...THOUGH THEY
WILL SLIDE INTO NW INDIANA ON SATURDAY AS NORTHERLY FLOW BECOMES
JUST WEST OF DUE NORTH. SKIES SHOULD START TO CLEAR BY DAYBREAK OVER
THE NW CWA...SO TEMPERATURES SHOULD DROP PRETTY WELL THERE GIVEN
THE GOOD RADIATION COOLING...PROBABLY INTO THE MID TEENS.
OUTSIDE OF LAKE EFFECT CONCERNS...THE ONLY FOCUS OVER THE WEEKEND
WAS TEMPERATURES WITH HIGH PRESSURE BUILDING OVERHEAD. FOR HIGHS
ON SATURDAY...SUSPECT THAT THE MARCH SUN WILL GO TO WORK ON THE
SNOW COVER...ESPECIALLY FOR AREAS THAT DIDNT SEE MUCH THIS WEEK.
FOR MARCH 1-15...WITH 850 TEMPS AROUND -10C AS IS PROGGED ON
SATURDAY...MEDIAN HIGH AT ORD IS 34 DEGREES. WENT JUST UNDER THAT
IN NORTHERN CWA/ESPECIALLY IN THE NORTHEAST WHERE SNOW PACK IS
DEEPEST...YIELDING HIGHS AROUND 30. TO THE SOUTH OF I-80...SUSPECT
WE`LL SEE SOME MID TO EVEN UPPER 30S AS SUN EATS AWAY AT MEAGER
SNOW COVER.
THEN SUNDAY NIGHT...THERE IS A STRONG SIGNAL FOR GOOD RADIATIONAL
COOLING...ESPECIALLY ON THE ECMWF...WHICH MAY BE A BIT TOO
AGGRESSIVE WITH ITS ZERO TO SLIGHTLY BELOW ZERO NUMBERS FOR NORTH
CENTRAL IL. BASICALLY CONTINUED IDEA OF PREVIOUS FORECAST WITH
POTENTIAL FOR SINGLE DIGIT LOWS WEST OF FOX RIVER. ON SUNDAY...THE
COLD START MAY KEEP TEMPS IN CHECK SOMEWHAT...BUT MARCH SUN ANGLE
AND LONGER DAYLIGHT HOURS EXPECTED TO COMPENSATE...IN ADDITION TO
SLIGHTLY WARMER TEMPS ALOFT. MEDIAN ORD HIGHS FOR DAYS WITH 850
TEMPS AS PROGGED ON SUNDAY IN -6 TO -8 RANGE IS 38. DIDNT GO THIS
MILD DUE TO COLD START AND SNOW COVER OVER NORTHERN CWA...BUT
BUMPED UP TEMPS A FEW DEGREES FROM PREVIOUS. IF SNOW COVER CAN BE
ELIMINATED ON SATURDAY OVER SOUTH...WOULDNT BE SURPRISED IF SOME
LOCATIONS TAG 40 DEGREES...BUT FOR NOW WENT WITH UPPER 30S IN
CENTRAL IL. INCREASING CLOUD COVER SHOULD RESULT IN LOWS SEVERAL
DEGREES WARMER SUNDAY NIGHT THAN SATURDAY NIGHT.
LONG TERM...MONDAY THROUGH THURSDAY
MAIN FOCUS IS ON VERY ENERGETIC CLIPPER SYSTEM EARLY NEXT WEEK.
THERE HAVE BEEN FAIRLY SIGNIFICANT RUN TO RUN CHANGES WITH THE
TIMING AND TRACK OF THE STRONG UPPER LOW AND SURFACE REFLECTION.
WOULD EXPECT THIS TO CONTINUE UNTIL UPPER WAVE MAKES LANDFALL IN
PACIFIC NORTHWEST SATURDAY NIGHT ALLOWING FOR SAMPLING BY RAOB
NETWORK. AS IT STANDS RIGHT NOW...00Z GUIDANCE HAS SHIFTED BACK
NORTH...WHICH WOULD PUT MOST OF CWA IN LINE FOR A POTENTIALLY
ACCUMULATING SNOW. COULD SEE THE START OF SOME WAA SNOWS AHEAD OF
SYSTEM ON MONDAY...SO BLENDED POPS WERE MAINTAINED.
HOWEVER...BIGGEST CHANGE WAS TO GREATLY INCREASE POPS ABOVE
ALLBLEND MONDAY NIGHT AND TUESDAY IN LINE WITH A SLOWER
PROGRESSION OF THE UPPER LOW AND ATTENDANT SURFACE LOW FAVORED BY
THE 00Z ECMWF...CANADIAN...GEFS AND HPC. GFS APPEARS MUCH TOO FAST
IN CLEARING THE SYSTEM OFF TO THE EAST. FOR NOW...BUMPED UP POPS
TO MID RANGE CHANCE GIVEN UNCERTAINTY.
AS CURRENTLY MODELED...THE UPPER LOW WITH THIS SYSTEM LOOKS QUITE
STRONG...WITH A TIGHT BAROCLINIC ZONE ALONG/AHEAD OF ITS TRACK. THUS
THERE COULD BE A NICE SWATH OF SNOW PUT DOWN SOMEWHERE OVER/NEAR THE
REGION. ON THE NEGATIVE SIDE...TEMPERATURES AS IS USUALLY THE CASE
IN MARCH WOULD BE NEAR FREEZING...SO THE SNOW WOULD HAVE TO COME
DOWN HARD TO ACCUMULATE EFFICIENTLY. LOTS OF TIME TO MONITOR THIS
SYSTEM.
FOR THE REST OF THE EXTENDED AND BEYOND...AFTER A FAIRLY COOL DAY ON
WEDNESDAY BEHIND THE EARLY WEEK SYSTEM...THERE COULD BE BRIEF WARM UP
TO NORMAL TO ABOVE NORMAL AS THE PATTERN TRANSITIONS FROM AN EASTERN
TROUGH/WESTERN RIDGE (POSITIVE PNA) CONFIGURATION TO A WESTERN
TROUGH/EASTERN RIDGE (NEGATIVE PNA) PATTERN. WITH RIDGING FIRST
AMPLIFYING INTO CENTER OF CONUS...WE COULD SEE A FEW DAYS OF
TEMPERATURES AT LEAST BACK INTO THE 40S.
HOWEVER...THE LONG RANGE ENSEMBLES LOOKING BEYOND THIS 7 DAY
FORECAST PERIOD ARE HOLDING ONTO THE IDEA OF MAINTAINING HIGH
LATITUDE BLOCKING/NEGATIVE NAO AND NEGATIVE AO THROUGH MID MARCH.
IN ADDITION...RIDGING MAY AMPLIFY OVER OR NEAR ALASKA WHICH ALLOWS
FRESH COLD AIR TO INFILTRATE CANADA AND THE NORTHERN CONUS. BOTTOM
LINE IS ANY WARM UP COULD BE QUICKLY FOLLOWED BY A RETURN TO THE
COLDER THAN NORMAL PATTERN. NO MARCH 2012 PATTERN IS SEEN IN THE
EXTENDED FOR ANYONE HOPING FOR AN EARLY SUMMER AGAIN.
RC
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 20Z...
* LOW MVFR CIGS IN THE 1000-1500 FT RANGE THIS AFTERNOON.
* LAKE EFFECT SNOW SHOWERS POSSIBLE AGAIN TONIGHT...LOWER MVFR VIS
POSSIBLE.
KJB
//DISCUSSION...UPDATED 18Z...
THE LAKE EFFECT SNOW SHOWER ACTIVITY CONTINUES TO ABATE ACROSS THE
TERMINALS EARLY THIS AFTERNOON AS THE LOWER LEVEL CONVERGENCE WEAKENS
IN RESPONSE TO AN INVERTED SURFACE TROUGH MOVING ONSHORE ACROSS
NORTHEASTERN ILLINOIS. WINDS ARE BECOMING NORTH-NORTHEASTERLY IN
THE WAKE OF THIS SURFACE TROUGH...AND I EXPECT ALL OF THE EASTERN
TERMINALS TO BE 010-020 BY OR SHORTLY AFTER 18 UTC. ANY ADDITIONAL
SNOW SHOWER ACTIVITY THIS AFTERNOON LOOKS TO BE VERY LIGHT...WITH
MINIMAL IMPACTS TO THE VISIBILITY EXPECTED.
THE SURFACE FLOW WILL REMAIN OUT OF THE NORTH NORTHEAST INTO
SATURDAY AS A SURFACE RIDGE OF HIGH PRESSURE CONTINUES TO BUILD
EASTWARD ACROSS THE REGION. SOME ADDITIONAL LAKE EFFECT SNOW
SHOWER ACTIVITY IS POSSIBLY TONIGHT ACROSS THE EASTERN TERMINALS
AS THE LAKESHORE CONVERGENCE INCREASES IN RESPONSE TO A LAND BREEZE.
HOWEVER...THE OVERALL THERMODYNAMIC SETUP IS SLOWLY BECOMING
SLIGHTLY LESS FAVORABLE FOR LAKE EFFECT SNOW. THUS ONLY SOME MVFR
VIS IS CURRENTLY EXPECTED...WITH A SMALL POSSIBILITY OF A SHORT
PERIOD OF LOWER VIS NOT OUT OF THE QUESTION TONIGHT.
KJB
//ORD AND MDW CONFIDENCE...UPDATED 20Z...
* LOW TO MEDIUM CONFIDENCE ON ADDITIONAL LAKE EFFECT SNOW SHOWERS TONIGHT.
* HIGH CONFIDENCE IN LOW MVFR CIGS THROUGH THE AFTERNOON.
KJB
//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...
SATURDAY NIGHT...MVFR CIGS POSSIBLE EARLY.
SUNDAY...VFR.
MONDAY...CHANCE OF LIGHT SNOW IN THE AFTERNOON. MVFR POSSIBLE
LATE.
MONDAY NIGHT INTO TUESDAY...GOOD CHANCE OF SNOW. IFR PROBABLE.
WEDNESDAY...MVFR CIGS POSSIBLE.
THURSDAY...VFR EXPECTED.
IZZI
&&
.MARINE...
222 PM CST
NORTH WINDS WILL CONTINUE TO GRADUALLY DIMINISH TONIGHT THROUGH
SUNDAY AS A LOW IN THE NORTH ATLANTIC EAST OF THE CANADIAN
MARITIMES CONTINUES TO MOVE FURTHER OUT TO SEA. THIS ALLOWS A
RIDGE OF HIGH PRESSURE TO GRADUALLY SHIFT EASTWARD FROM THE
PLAINS...BUT THE RIDGE WILL NOT REACH LAKE MI UNTIL LATER
SATURDAY AND SATURDAY EVENING RESULTING IN PERIOD OF LIGHT
VARIABLE WINDS BEFORE BECOMING EAST AND SOUTHEAST BY MONDAY
MORNING AS THE RIDGE CONTINUES ITS SLOW DRIFT TO THE EAST INTO
THE CENTRAL GREAT LAKES AND A LOW MOVES FROM THE ROCKIES OVER THE
HIGH PLAINS TO THE CENTRAL PLAINS. THE SOUTHEAST AND EAST WINDS
WILL BE INCREASING TO MODERATE BREEZES BY MONDAY AS THE LOW
CONTINUES EAST TO THE LOWER OH VALLEY REGION.
TRS
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL 3 AM
SUNDAY.
SMALL CRAFT ADVISORY...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL 9 AM SUNDAY.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
147 PM CST FRI MAR 1 2013
.DISCUSSION...
919 AM CST
UPDATED THE GRIDS FOR THIS MORNING...MAINLY TO ACCOUNT FOR ONGOING
LAKE EFFECT SNOW SHOWERS.
LATEST RADAR IMAGERY DEPICTING SOME LIGHT RETURNS ACROSS ALL OF
NORTHERN ILLINOIS WITH AN ISOLATED AREA OF FAIRLY DECENT
RETURNS...PRIMARILY ACROSS SOUTHEAST COOK COUNTY AND NORTHWEST
LAKE COUNTY IN INDIANA. UNDER THE LIGHTER RETURNS LIGHT SNOW
CONTINUES WITH VIS STAYING CONFINED TO ONLY THE 3-6 MILE
RANGE...WITH VIS LIKELY AT OR UNDER 1 MILE UNDER THE STRONGER
RETURNS. THESE SNOW SHOWERS ARE IN RESPONSE TO PERSISTENT
NORTH/NORTHEAST FLOW OFF OF A MODERATELY UNSTABLE LAKE...AS WELL
AS WEAK LARGE SCALE LIFT. LATEST SURFACE ANALYSIS INDICATING A
SURFACE TROUGH SITUATED ACROSS THE SOUTHERN HALF OF THE
LAKE...EXTENDING BACK NORTHWEST FROM A WEAK SURFACE LOW OVER
IN/KY. THIS HAS RESULTED IN AN AREA OF BETTER CONVERGENCE THIS
MORNING...WHICH HAS THEN PROVIDED THIS ISOLATED AREA OF STRONGER
SNOW SHOWERS. LATEST SHORT TERM GUIDANCE IS INDICATING THIS TROUGH
TO SLOWLY EXIT/DAMPEN WITH ALL SURFACE WINDS BECOMING MORE
NORTHERLY...AND LOSS OF BETTER CONVERGENCE. SO DO EXPECT THIS
ISOLATED AREA OF STRONGER SNOW SHOWERS TO PERSIST OVER THE NEXT
COUPLE OF HOURS...ONCE AGAIN PRIMARILY AFFECTING ONLY SOUTHEAST
COOK AND NORTHWEST LAKE COUNTY IN INDIANA. UNDER THESE STRONGER
RETURNS IT WOULD NOT BE OUT OF THE QUESTION FOR SOME ADDITIONAL
ACCUMULATIONS...WITH 1 TO 3 INCHES NOT OF THE REALM OF
POSSIBILITY THROUGH MID DAY. LIGHT SNOW SHOWERS ARE THEN EXPECTED
TO CONTINUE INTO THE AFTERNOON...BUT WITH ONLY LIGHT ACCUMULATIONS
ANTICIPATED.
RODRIGUEZ
//PREV DISCUSSION...
330 AM CST
FORECAST CONCERNS ARE LAKE EFFECT SNOW SHOWER POTENTIAL THE NEXT FEW
DAYS...COLD TEMPERATURES OVER THE WEEKEND...AND A POSSIBLE SNOW
PRODUCING SYSTEM EARLY NEXT WEEK.
SHORT TERM...TODAY THROUGH SUNDAY NIGHT...
SLIGHTLY COLDER AIR MASS WILL SETTLE OVER THE REGION TODAY ON
CONTINUED NORTHERLY FLOW...WITH A LARGE AREA OF HIGH PRESSURE
BUILDING IN FROM THE NORTH. THIS SHOULD KEEP HIGHS A FEW DEGREES
COOLER THAN YESTERDAY. LAKE EFFECT SET UP IS QUITE MARGINAL
THERMODYNAMICALLY...BUT COMPENSATING SOMEWHAT WILL BE GOOD
CONVERGENCE AND FETCH WITH NORTH-NORTHEAST LOW LEVEL FLOW. THE
CONVERGENCE AND EVEN SOME ENHANCED LIFT IS BEST ALIGNED OVER
ILLINOIS AND PORTION OF NW INDIANA LAKEFRONT THROUGH MID/LATE
MORNING...SO BUMPED UP POPS SOME FROM PREVIOUS FORECAST. COULD SEE
SOME VERY LIGHT ACCUMULATIONS. OUTSIDE OF LAKE EFFECT...THERE MAY BE
SOME FLURRIES INLAND. ALTHOUGH STRATUS CAN CLEAR OUT QUICKER THIS
TIME OF YEAR DUE TO HIGHER SUN ANGLE...THINK THE NAM IS BEING WAY
TOO AGGRESSIVE WITH CLEARING TREND FROM NORTH. USED RAP GUIDANCE FOR
NEAR TERM SKY FORECAST. MOST OF CWA SHOULD SEE OVC THROUGH DAYLIGHT
HOURS.
THE SAME GENERAL IDEA OF DECENT CONVERGENCE BUT VERY MARGINAL
THERMODYNAMICS AND INVERSION HEIGHTS CONTINUES THROUGH SATURDAY WITH
THE LAKE EFFECT. WILL CONTINUE TO CARRY CHANCE POPS...THOUGH THEY
WILL SLIDE INTO NW INDIANA ON SATURDAY AS NORTHERLY FLOW BECOMES
JUST WEST OF DUE NORTH. SKIES SHOULD START TO CLEAR BY DAYBREAK OVER
THE NW CWA...SO TEMPERATURES SHOULD DROP PRETTY WELL THERE GIVEN
THE GOOD RADIATION COOLING...PROBABLY INTO THE MID TEENS.
OUTSIDE OF LAKE EFFECT CONCERNS...THE ONLY FOCUS OVER THE WEEKEND
WAS TEMPERATURES WITH HIGH PRESSURE BUILDING OVERHEAD. FOR HIGHS
ON SATURDAY...SUSPECT THAT THE MARCH SUN WILL GO TO WORK ON THE
SNOW COVER...ESPECIALLY FOR AREAS THAT DIDNT SEE MUCH THIS WEEK.
FOR MARCH 1-15...WITH 850 TEMPS AROUND -10C AS IS PROGGED ON
SATURDAY...MEDIAN HIGH AT ORD IS 34 DEGREES. WENT JUST UNDER THAT
IN NORTHERN CWA/ESPECIALLY IN THE NORTHEAST WHERE SNOW PACK IS
DEEPEST...YIELDING HIGHS AROUND 30. TO THE SOUTH OF I-80...SUSPECT
WE`LL SEE SOME MID TO EVEN UPPER 30S AS SUN EATS AWAY AT MEAGER
SNOW COVER.
THEN SUNDAY NIGHT...THERE IS A STRONG SIGNAL FOR GOOD RADIATIONAL
COOLING...ESPECIALLY ON THE ECMWF...WHICH MAY BE A BIT TOO
AGGRESSIVE WITH ITS ZERO TO SLIGHTLY BELOW ZERO NUMBERS FOR NORTH
CENTRAL IL. BASICALLY CONTINUED IDEA OF PREVIOUS FORECAST WITH
POTENTIAL FOR SINGLE DIGIT LOWS WEST OF FOX RIVER. ON SUNDAY...THE
COLD START MAY KEEP TEMPS IN CHECK SOMEWHAT...BUT MARCH SUN ANGLE
AND LONGER DAYLIGHT HOURS EXPECTED TO COMPENSATE...IN ADDITION TO
SLIGHTLY WARMER TEMPS ALOFT. MEDIAN ORD HIGHS FOR DAYS WITH 850
TEMPS AS PROGGED ON SUNDAY IN -6 TO -8 RANGE IS 38. DIDNT GO THIS
MILD DUE TO COLD START AND SNOW COVER OVER NORTHERN CWA...BUT
BUMPED UP TEMPS A FEW DEGREES FROM PREVIOUS. IF SNOW COVER CAN BE
ELIMINATED ON SATURDAY OVER SOUTH...WOULDNT BE SURPRISED IF SOME
LOCATIONS TAG 40 DEGREES...BUT FOR NOW WENT WITH UPPER 30S IN
CENTRAL IL. INCREASING CLOUD COVER SHOULD RESULT IN LOWS SEVERAL
DEGREES WARMER SUNDAY NIGHT THAN SATURDAY NIGHT.
LONG TERM...MONDAY THROUGH THURSDAY
MAIN FOCUS IS ON VERY ENERGETIC CLIPPER SYSTEM EARLY NEXT WEEK.
THERE HAVE BEEN FAIRLY SIGNIFICANT RUN TO RUN CHANGES WITH THE
TIMING AND TRACK OF THE STRONG UPPER LOW AND SURFACE REFLECTION.
WOULD EXPECT THIS TO CONTINUE UNTIL UPPER WAVE MAKES LANDFALL IN
PACIFIC NORTHWEST SATURDAY NIGHT ALLOWING FOR SAMPLING BY RAOB
NETWORK. AS IT STANDS RIGHT NOW...00Z GUIDANCE HAS SHIFTED BACK
NORTH...WHICH WOULD PUT MOST OF CWA IN LINE FOR A POTENTIALLY
ACCUMULATING SNOW. COULD SEE THE START OF SOME WAA SNOWS AHEAD OF
SYSTEM ON MONDAY...SO BLENDED POPS WERE MAINTAINED.
HOWEVER...BIGGEST CHANGE WAS TO GREATLY INCREASE POPS ABOVE
ALLBLEND MONDAY NIGHT AND TUESDAY IN LINE WITH A SLOWER
PROGRESSION OF THE UPPER LOW AND ATTENDANT SURFACE LOW FAVORED BY
THE 00Z ECMWF...CANADIAN...GEFS AND HPC. GFS APPEARS MUCH TOO FAST
IN CLEARING THE SYSTEM OFF TO THE EAST. FOR NOW...BUMPED UP POPS
TO MID RANGE CHANCE GIVEN UNCERTAINTY.
AS CURRENTLY MODELED...THE UPPER LOW WITH THIS SYSTEM LOOKS QUITE
STRONG...WITH A TIGHT BAROCLINIC ZONE ALONG/AHEAD OF ITS TRACK. THUS
THERE COULD BE A NICE SWATH OF SNOW PUT DOWN SOMEWHERE OVER/NEAR THE
REGION. ON THE NEGATIVE SIDE...TEMPERATURES AS IS USUALLY THE CASE
IN MARCH WOULD BE NEAR FREEZING...SO THE SNOW WOULD HAVE TO COME
DOWN HARD TO ACCUMULATE EFFICIENTLY. LOTS OF TIME TO MONITOR THIS
SYSTEM.
FOR THE REST OF THE EXTENDED AND BEYOND...AFTER A FAIRLY COOL DAY ON
WEDNESDAY BEHIND THE EARLY WEEK SYSTEM...THERE COULD BE BRIEF WARM UP
TO NORMAL TO ABOVE NORMAL AS THE PATTERN TRANSITIONS FROM AN EASTERN
TROUGH/WESTERN RIDGE (POSITIVE PNA) CONFIGURATION TO A WESTERN
TROUGH/EASTERN RIDGE (NEGATIVE PNA) PATTERN. WITH RIDGING FIRST
AMPLIFYING INTO CENTER OF CONUS...WE COULD SEE A FEW DAYS OF
TEMPERATURES AT LEAST BACK INTO THE 40S.
HOWEVER...THE LONG RANGE ENSEMBLES LOOKING BEYOND THIS 7 DAY
FORECAST PERIOD ARE HOLDING ONTO THE IDEA OF MAINTAINING HIGH
LATITUDE BLOCKING/NEGATIVE NAO AND NEGATIVE AO THROUGH MID MARCH.
IN ADDITION...RIDGING MAY AMPLIFY OVER OR NEAR ALASKA WHICH ALLOWS
FRESH COLD AIR TO INFILTRATE CANADA AND THE NORTHERN CONUS. BOTTOM
LINE IS ANY WARM UP COULD BE QUICKLY FOLLOWED BY A RETURN TO THE
COLDER THAN NORMAL PATTERN. NO MARCH 2012 PATTERN IS SEEN IN THE
EXTENDED FOR ANYONE HOPING FOR AN EARLY SUMMER AGAIN.
RC
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 20Z...
* LOW MVFR CIGS IN THE 1000-1500 FT RANGE THIS AFTERNOON.
* LAKE EFFECT SNOW SHOWERS POSSIBLE AGAIN TONIGHT...LOWER MVFR VIS
POSSIBLE.
KJB
//DISCUSSION...UPDATED 18Z...
THE LAKE EFFECT SNOW SHOWER ACTIVITY CONTINUES TO ABATE ACROSS THE
TERMINALS EARLY THIS AFTERNOON AS THE LOWER LEVEL CONVERGENCE WEAKENS
IN RESPONSE TO AN INVERTED SURFACE TROUGH MOVING ONSHORE ACROSS
NORTHEASTERN ILLINOIS. WINDS ARE BECOMING NORTH-NORTHEASTERLY IN
THE WAKE OF THIS SURFACE TROUGH...AND I EXPECT ALL OF THE EASTERN
TERMINALS TO BE 010-020 BY OR SHORTLY AFTER 18 UTC. ANY ADDITIONAL
SNOW SHOWER ACTIVITY THIS AFTERNOON LOOKS TO BE VERY LIGHT...WITH
MINIMAL IMPACTS TO THE VISIBILITY EXPECTED.
THE SURFACE FLOW WILL REMAIN OUT OF THE NORTH NORTHEAST INTO
SATURDAY AS A SURFACE RIDGE OF HIGH PRESSURE CONTINUES TO BUILD
EASTWARD ACROSS THE REGION. SOME ADDITIONAL LAKE EFFECT SNOW
SHOWER ACTIVITY IS POSSIBLY TONIGHT ACROSS THE EASTERN TERMINALS
AS THE LAKESHORE CONVERGENCE INCREASES IN RESPONSE TO A LAND BREEZE.
HOWEVER...THE OVERALL THERMODYNAMIC SETUP IS SLOWLY BECOMING
SLIGHTLY LESS FAVORABLE FOR LAKE EFFECT SNOW. THUS ONLY SOME MVFR
VIS IS CURRENTLY EXPECTED...WITH A SMALL POSSIBILITY OF A SHORT
PERIOD OF LOWER VIS NOT OUT OF THE QUESTION TONIGHT.
KJB
//ORD AND MDW CONFIDENCE...UPDATED 20Z...
* LOW TO MEDIUM CONFIDENCE ON ADDITIONAL LAKE EFFECT SNOW SHOWERS TONIGHT.
* HIGH CONFIDENCE IN LOW MVFR CIGS THROUGH THE AFTERNOON.
KJB
//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...
SATURDAY NIGHT...MVFR CIGS POSSIBLE EARLY.
SUNDAY...VFR.
MONDAY...CHANCE OF LIGHT SNOW IN THE AFTERNOON. MVFR POSSIBLE
LATE.
MONDAY NIGHT INTO TUESDAY...GOOD CHANCE OF SNOW. IFR PROBABLE.
WEDNESDAY...MVFR CIGS POSSIBLE.
THURSDAY...VFR EXPECTED.
IZZI
&&
.MARINE...
222 AM CST
MODERATELY STRONG NORTH WINDS LIKELY TO CONTINUE THROUGH SATURDAY
WITH OCCASIONAL GALE FORCE GUSTS A POSSIBILITY...ESPECIALLY LATER
THIS AFTERNOON INTO THE EVENING...BUT GENERALLY THINK ANY GALES
WILL BE INFREQUENT ENOUGH TO KEEP OUT OF THE FORECAST. WINDS WILL
BEGIN TO DIMINISHING LATER SATURDAY INTO SUNDAY AS RIDGE AXIS
APPROACHES AND THEN MOVES ACROSS THE LAKE SUNDAY NIGHT. ANOTHER
SYSTEM WILL PASS TO THE SOUTHWEST OF THE LAKE EARLY/MIDDLE PART OF
NEXT WEEK WITH WINDS FRESHENING UP A BIT...BUT SYSTEM SHOULD BE
WEAK ENOUGH AND FAR ENOUGH AWAY TO NOT CAUSE ANY MAJOR
WINDS/WAVES.
IZZI
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL 3 AM
SUNDAY.
SMALL CRAFT ADVISORY...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL 9 AM SUNDAY.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1146 AM CST FRI MAR 1 2013
.DISCUSSION...
919 AM CST
UPDATED THE GRIDS FOR THIS MORNING...MAINLY TO ACCOUNT FOR ONGOING
LAKE EFFECT SNOW SHOWERS.
LATEST RADAR IMAGERY DEPICTING SOME LIGHT RETURNS ACROSS ALL OF
NORTHERN ILLINOIS WITH AN ISOLATED AREA OF FAIRLY DECENT
RETURNS...PRIMARILY ACROSS SOUTHEAST COOK COUNTY AND NORTHWEST
LAKE COUNTY IN INDIANA. UNDER THE LIGHTER RETURNS LIGHT SNOW
CONTINUES WITH VIS STAYING CONFINED TO ONLY THE 3-6 MILE
RANGE...WITH VIS LIKELY AT OR UNDER 1 MILE UNDER THE STRONGER
RETURNS. THESE SNOW SHOWERS ARE IN RESPONSE TO PERSISTENT
NORTH/NORTHEAST FLOW OFF OF A MODERATELY UNSTABLE LAKE...AS WELL
AS WEAK LARGE SCALE LIFT. LATEST SURFACE ANALYSIS INDICATING A
SURFACE TROUGH SITUATED ACROSS THE SOUTHERN HALF OF THE
LAKE...EXTENDING BACK NORTHWEST FROM A WEAK SURFACE LOW OVER
IN/KY. THIS HAS RESULTED IN AN AREA OF BETTER CONVERGENCE THIS
MORNING...WHICH HAS THEN PROVIDED THIS ISOLATED AREA OF STRONGER
SNOW SHOWERS. LATEST SHORT TERM GUIDANCE IS INDICATING THIS TROUGH
TO SLOWLY EXIT/DAMPEN WITH ALL SURFACE WINDS BECOMING MORE
NORTHERLY...AND LOSS OF BETTER CONVERGENCE. SO DO EXPECT THIS
ISOLATED AREA OF STRONGER SNOW SHOWERS TO PERSIST OVER THE NEXT
COUPLE OF HOURS...ONCE AGAIN PRIMARILY AFFECTING ONLY SOUTHEAST
COOK AND NORTHWEST LAKE COUNTY IN INDIANA. UNDER THESE STRONGER
RETURNS IT WOULD NOT BE OUT OF THE QUESTION FOR SOME ADDITIONAL
ACCUMULATIONS...WITH 1 TO 3 INCHES NOT OF THE REALM OF
POSSIBILITY THROUGH MID DAY. LIGHT SNOW SHOWERS ARE THEN EXPECTED
TO CONTINUE INTO THE AFTERNOON...BUT WITH ONLY LIGHT ACCUMULATIONS
ANTICIPATED.
RODRIGUEZ
//PREV DISCUSSION...
330 AM CST
FORECAST CONCERNS ARE LAKE EFFECT SNOW SHOWER POTENTIAL THE NEXT FEW
DAYS...COLD TEMPERATURES OVER THE WEEKEND...AND A POSSIBLE SNOW
PRODUCING SYSTEM EARLY NEXT WEEK.
SHORT TERM...TODAY THROUGH SUNDAY NIGHT...
SLIGHTLY COLDER AIR MASS WILL SETTLE OVER THE REGION TODAY ON
CONTINUED NORTHERLY FLOW...WITH A LARGE AREA OF HIGH PRESSURE
BUILDING IN FROM THE NORTH. THIS SHOULD KEEP HIGHS A FEW DEGREES
COOLER THAN YESTERDAY. LAKE EFFECT SET UP IS QUITE MARGINAL
THERMODYNAMICALLY...BUT COMPENSATING SOMEWHAT WILL BE GOOD
CONVERGENCE AND FETCH WITH NORTH-NORTHEAST LOW LEVEL FLOW. THE
CONVERGENCE AND EVEN SOME ENHANCED LIFT IS BEST ALIGNED OVER
ILLINOIS AND PORTION OF NW INDIANA LAKEFRONT THROUGH MID/LATE
MORNING...SO BUMPED UP POPS SOME FROM PREVIOUS FORECAST. COULD SEE
SOME VERY LIGHT ACCUMULATIONS. OUTSIDE OF LAKE EFFECT...THERE MAY BE
SOME FLURRIES INLAND. ALTHOUGH STRATUS CAN CLEAR OUT QUICKER THIS
TIME OF YEAR DUE TO HIGHER SUN ANGLE...THINK THE NAM IS BEING WAY
TOO AGGRESSIVE WITH CLEARING TREND FROM NORTH. USED RAP GUIDANCE FOR
NEAR TERM SKY FORECAST. MOST OF CWA SHOULD SEE OVC THROUGH DAYLIGHT
HOURS.
THE SAME GENERAL IDEA OF DECENT CONVERGENCE BUT VERY MARGINAL
THERMODYNAMICS AND INVERSION HEIGHTS CONTINUES THROUGH SATURDAY WITH
THE LAKE EFFECT. WILL CONTINUE TO CARRY CHANCE POPS...THOUGH THEY
WILL SLIDE INTO NW INDIANA ON SATURDAY AS NORTHERLY FLOW BECOMES
JUST WEST OF DUE NORTH. SKIES SHOULD START TO CLEAR BY DAYBREAK OVER
THE NW CWA...SO TEMPERATURES SHOULD DROP PRETTY WELL THERE GIVEN
THE GOOD RADIATION COOLING...PROBABLY INTO THE MID TEENS.
OUTSIDE OF LAKE EFFECT CONCERNS...THE ONLY FOCUS OVER THE WEEKEND
WAS TEMPERATURES WITH HIGH PRESSURE BUILDING OVERHEAD. FOR HIGHS
ON SATURDAY...SUSPECT THAT THE MARCH SUN WILL GO TO WORK ON THE
SNOW COVER...ESPECIALLY FOR AREAS THAT DIDNT SEE MUCH THIS WEEK.
FOR MARCH 1-15...WITH 850 TEMPS AROUND -10C AS IS PROGGED ON
SATURDAY...MEDIAN HIGH AT ORD IS 34 DEGREES. WENT JUST UNDER THAT
IN NORTHERN CWA/ESPECIALLY IN THE NORTHEAST WHERE SNOW PACK IS
DEEPEST...YIELDING HIGHS AROUND 30. TO THE SOUTH OF I-80...SUSPECT
WE`LL SEE SOME MID TO EVEN UPPER 30S AS SUN EATS AWAY AT MEAGER
SNOW COVER.
THEN SUNDAY NIGHT...THERE IS A STRONG SIGNAL FOR GOOD RADIATIONAL
COOLING...ESPECIALLY ON THE ECMWF...WHICH MAY BE A BIT TOO
AGGRESSIVE WITH ITS ZERO TO SLIGHTLY BELOW ZERO NUMBERS FOR NORTH
CENTRAL IL. BASICALLY CONTINUED IDEA OF PREVIOUS FORECAST WITH
POTENTIAL FOR SINGLE DIGIT LOWS WEST OF FOX RIVER. ON SUNDAY...THE
COLD START MAY KEEP TEMPS IN CHECK SOMEWHAT...BUT MARCH SUN ANGLE
AND LONGER DAYLIGHT HOURS EXPECTED TO COMPENSATE...IN ADDITION TO
SLIGHTLY WARMER TEMPS ALOFT. MEDIAN ORD HIGHS FOR DAYS WITH 850
TEMPS AS PROGGED ON SUNDAY IN -6 TO -8 RANGE IS 38. DIDNT GO THIS
MILD DUE TO COLD START AND SNOW COVER OVER NORTHERN CWA...BUT
BUMPED UP TEMPS A FEW DEGREES FROM PREVIOUS. IF SNOW COVER CAN BE
ELIMINATED ON SATURDAY OVER SOUTH...WOULDNT BE SURPRISED IF SOME
LOCATIONS TAG 40 DEGREES...BUT FOR NOW WENT WITH UPPER 30S IN
CENTRAL IL. INCREASING CLOUD COVER SHOULD RESULT IN LOWS SEVERAL
DEGREES WARMER SUNDAY NIGHT THAN SATURDAY NIGHT.
LONG TERM...MONDAY THROUGH THURSDAY
MAIN FOCUS IS ON VERY ENERGETIC CLIPPER SYSTEM EARLY NEXT WEEK.
THERE HAVE BEEN FAIRLY SIGNIFICANT RUN TO RUN CHANGES WITH THE
TIMING AND TRACK OF THE STRONG UPPER LOW AND SURFACE REFLECTION.
WOULD EXPECT THIS TO CONTINUE UNTIL UPPER WAVE MAKES LANDFALL IN
PACIFIC NORTHWEST SATURDAY NIGHT ALLOWING FOR SAMPLING BY RAOB
NETWORK. AS IT STANDS RIGHT NOW...00Z GUIDANCE HAS SHIFTED BACK
NORTH...WHICH WOULD PUT MOST OF CWA IN LINE FOR A POTENTIALLY
ACCUMULATING SNOW. COULD SEE THE START OF SOME WAA SNOWS AHEAD OF
SYSTEM ON MONDAY...SO BLENDED POPS WERE MAINTAINED.
HOWEVER...BIGGEST CHANGE WAS TO GREATLY INCREASE POPS ABOVE
ALLBLEND MONDAY NIGHT AND TUESDAY IN LINE WITH A SLOWER
PROGRESSION OF THE UPPER LOW AND ATTENDANT SURFACE LOW FAVORED BY
THE 00Z ECMWF...CANADIAN...GEFS AND HPC. GFS APPEARS MUCH TOO FAST
IN CLEARING THE SYSTEM OFF TO THE EAST. FOR NOW...BUMPED UP POPS
TO MID RANGE CHANCE GIVEN UNCERTAINTY.
AS CURRENTLY MODELED...THE UPPER LOW WITH THIS SYSTEM LOOKS QUITE
STRONG...WITH A TIGHT BAROCLINIC ZONE ALONG/AHEAD OF ITS TRACK. THUS
THERE COULD BE A NICE SWATH OF SNOW PUT DOWN SOMEWHERE OVER/NEAR THE
REGION. ON THE NEGATIVE SIDE...TEMPERATURES AS IS USUALLY THE CASE
IN MARCH WOULD BE NEAR FREEZING...SO THE SNOW WOULD HAVE TO COME
DOWN HARD TO ACCUMULATE EFFICIENTLY. LOTS OF TIME TO MONITOR THIS
SYSTEM.
FOR THE REST OF THE EXTENDED AND BEYOND...AFTER A FAIRLY COOL DAY ON
WEDNESDAY BEHIND THE EARLY WEEK SYSTEM...THERE COULD BE BRIEF WARM UP
TO NORMAL TO ABOVE NORMAL AS THE PATTERN TRANSITIONS FROM AN EASTERN
TROUGH/WESTERN RIDGE (POSITIVE PNA) CONFIGURATION TO A WESTERN
TROUGH/EASTERN RIDGE (NEGATIVE PNA) PATTERN. WITH RIDGING FIRST
AMPLIFYING INTO CENTER OF CONUS...WE COULD SEE A FEW DAYS OF
TEMPERATURES AT LEAST BACK INTO THE 40S.
HOWEVER...THE LONG RANGE ENSEMBLES LOOKING BEYOND THIS 7 DAY
FORECAST PERIOD ARE HOLDING ONTO THE IDEA OF MAINTAINING HIGH
LATITUDE BLOCKING/NEGATIVE NAO AND NEGATIVE AO THROUGH MID MARCH.
IN ADDITION...RIDGING MAY AMPLIFY OVER OR NEAR ALASKA WHICH ALLOWS
FRESH COLD AIR TO INFILTRATE CANADA AND THE NORTHERN CONUS. BOTTOM
LINE IS ANY WARM UP COULD BE QUICKLY FOLLOWED BY A RETURN TO THE
COLDER THAN NORMAL PATTERN. NO MARCH 2012 PATTERN IS SEEN IN THE
EXTENDED FOR ANYONE HOPING FOR AN EARLY SUMMER AGAIN.
RC
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 18Z...
* WINDS BECOMING NORTH-NORTHEAST EARLY THIS AFTERNOON.
* MVFR CIGS.
* LAKE EFFECT SNOW SHOWERS POSSIBLE AGAIN TONIGHT...LOWER MVFR VIS
POSSIBLE.
KJB
//DISCUSSION...UPDATED 18Z...
THE LAKE EFFECT SNOW SHOWER ACTIVITY CONTINUES TO ABATE ACROSS THE
TERMINALS EARLY THIS AFTERNOON AS THE LOWER LEVEL CONVERGENCE WEAKENS
IN RESPONSE TO AN INVERTED SURFACE TROUGH MOVING ONSHORE ACROSS
NORTHEASTERN ILLINOIS. WINDS ARE BECOMING NORTH-NORTHEASTERLY IN
THE WAKE OF THIS SURFACE TROUGH...AND I EXPECT ALL OF THE EASTERN
TERMINALS TO BE 010-020 BY OR SHORTLY AFTER 18 UTC. ANY ADDITIONAL
SNOW SHOWER ACTIVITY THIS AFTERNOON LOOKS TO BE VERY LIGHT...WITH
MINIMAL IMPACTS TO THE VISIBILITY EXPECTED.
THE SURFACE FLOW WILL REMAIN OUT OF THE NORTH NORTHEAST INTO
SATURDAY AS A SURFACE RIDGE OF HIGH PRESSURE CONTINUES TO BUILD
EASTWARD ACROSS THE REGION. SOME ADDITIONAL LAKE EFFECT SNOW
SHOWER ACTIVITY IS POSSIBLY TONIGHT ACROSS THE EASTERN TERMINALS
AS THE LAKESHORE CONVERGENCE INCREASES IN RESPONSE TO A LAND BREEZE.
HOWEVER...THE OVERALL THERMODYNAMIC SETUP IS SLOWLY BECOMING
SLIGHTLY LESS FAVORABLE FOR LAKE EFFECT SNOW. THUS ONLY SOME MVFR
VIS IS CURRENTLY EXPECTED...WITH A SMALL POSSIBILITY OF A SHORT
PERIOD OF LOWER VIS NOT OUT OF THE QUESTION TONIGHT.
KJB
//ORD AND MDW CONFIDENCE...UPDATED 18Z...
* MEDIUM TO HIGH CONFIDENCE ON NORTH-NORTHEAST WINDS THROUGH THIS AFTERNOON.
* LOW TO MEDIUM CONFIDENCE ON ADDITIONAL LAKE EFFECT SNOW SHOWERS TONIGHT.
KJB
//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...
SATURDAY NIGHT...MVFR CIGS POSSIBLE EARLY.
SUNDAY...VFR.
MONDAY...CHANCE OF LIGHT SNOW IN THE AFTERNOON. MVFR POSSIBLE
LATE.
MONDAY NIGHT INTO TUESDAY...GOOD CHANCE OF SNOW. IFR PROBABLE.
WEDNESDAY...MVFR CIGS POSSIBLE.
THURSDAY...VFR EXPECTED.
IZZI
&&
.MARINE...
222 AM CST
MODERATELY STRONG NORTH WINDS LIKELY TO CONTINUE THROUGH SATURDAY
WITH OCCASIONAL GALE FORCE GUSTS A POSSIBILITY...ESPECIALLY LATER
THIS AFTERNOON INTO THE EVENING...BUT GENERALLY THINK ANY GALES
WILL BE INFREQUENT ENOUGH TO KEEP OUT OF THE FORECAST. WINDS WILL
BEGIN TO DIMINISHING LATER SATURDAY INTO SUNDAY AS RIDGE AXIS
APPROACHES AND THEN MOVES ACROSS THE LAKE SUNDAY NIGHT. ANOTHER
SYSTEM WILL PASS TO THE SOUTHWEST OF THE LAKE EARLY/MIDDLE PART OF
NEXT WEEK WITH WINDS FRESHENING UP A BIT...BUT SYSTEM SHOULD BE
WEAK ENOUGH AND FAR ENOUGH AWAY TO NOT CAUSE ANY MAJOR
WINDS/WAVES.
IZZI
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL 3 AM
SUNDAY.
SMALL CRAFT ADVISORY...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL 9 AM SUNDAY.
&&
$$
AREA FORECAST DISCUSSION
NWS INDIANAPOLIS IN
531 PM EST FRI MAR 1 2013
.UPDATE...
THE AVIATION SECTION HAS BEEN UPDATED BELOW.
&&
.SYNOPSIS...
ISSUED AT 257 PM EST FRI MAR 1 2013
ONE LAST DISTURBANCE SLIDING AROUND THE PERIPHERY OF THE LARGE UPPER
LOW TO THE NORTHEAST WILL PUSH THROUGH THE REGION EARLY THIS
EVENING...WITH CONTINUED POTENTIAL FOR LIGHT SNOW SHOWERS OR
FLURRIES IN PORTIONS OF THE SOUTHERN FORECAST AREA. HIGH PRESSURE AT
THE SURFACE WILL RETURN DRY WEATHER TO THE AREA THROUGH THE WEEKEND.
ANOTHER DISTURBANCE IN NORTHWEST FLOW ALOFT MAY PUSH THROUGH THE
AREA EARLY NEXT WEEK...MONDAY NIGHT THROUGH TUESDAY NIGHT WITH
ADDITIONAL PRECIPITATION CHANCES ASSOCIATED WITH IT. HIGH
PRESSURE...DRY WEATHER AND WARMER TEMPERATURES ARE IN STORE FOR THE
END OF NEXT WEEK.
&&
.NEAR TERM /TONIGHT/...
ISSUED AT 257 PM EST FRI MAR 1 2013
PER LATEST RADAR MOSAIC TRENDS AND MOST RECENT HRRR RUN DEPICT SNOW
SHOWERS/FLURRIES AND EVEN SOME DRIZZLE ACROSS THE SOUTH WILL BE A
LITTLE SLOWER IN EXITING THE FORECAST AREA. LEFT IN LOW CHANCES FOR
PRECIP ACROSS THE SOUTH FOR THIS EVENING...THEN WENT DRY FOR THE
OVERNIGHT. BASED ON PERSISTENCE AND THE FACT THAT CLOUDS AND EVEN TO
SOME EXTENT SOME PRECIPITATION WILL HANG AROUND A WHILE
LONGER...BUMPED UP OVERNIGHT LOWS ABOUT 5 DEGREES ABOVE MOS WHICH
YIELDS LOWS IN THE MID TO UPPER 20S.
&&
.SHORT TERM /SATURDAY THROUGH MONDAY/...
ISSUED AT 257 PM EST FRI MAR 1 2013
IT/S LOOKING LIKE A DRY WEEKEND. SURFACE HIGH PRESSURE WILL BUILD
OVER THE AREA AND REMAIN THE DOMINANT WEATHER FIXTURE FOR THE
WEEKEND. MOSTLY CLOUDY SKIES APPEAR TO LINGER OVER CENTRAL INDIANA
FOR THE FIRST HALF OF THE WEEKEND BUT THE COLUMN FINALLY BEGINS TO
DRY OUT BY SUNDAY...ALLOWING MOSTLY SUNNY TO PARTLY CLOUDY SKIES TO
RETURN TO THE AREA. NORTHERLY FLOW WILL KEEP TEMPERATURE BELOW
NORMAL THROUGH THE WEEKEND. NEXT SYSTEM TO IMPACT THE REGION COME
SOMETIME MONDAY OR MONDAY NIGHT. THERE A STARK DIFFERENCE WITH
RESPECT TO TIMING...WITH THE GFS BEING QUITE A FAST AND PROGRESSIVE
OUTLIER...SO LEANED TOWARD THE REST OF THE SLOWER GUIDANCE AND ONLY
INTRODUCED LOW CHANCE POPS LATE IN THE DAY MONDAY.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
ISSUED AT 257 PM EST FRI MAR 1 2013
THE EXTENDED PERIOD WILL START OUT RATHER ACTIVE AS A SURFACE LOW
FROM THE SOUTHERN PLAINS EVENTUALLY MERGES WITH AN UPPER LEVEL LOW
COMING OUT OF THE NORTHERN PLAINS ON TUESDAY. THE SURFACE LOW WILL
REACH CENTRAL INDIANA FIRST THOUGH BRINGING RAIN AND SNOW CHANCES ON
MONDAY. THE GFS AND EURO CONTINUE TO DIFFER ON TRACK OF UPPER LEVEL
LOW WITH THE GFS DIGGING IT FURTHER INTO THE TENNESSEE VALLEY WHILE
STRENGTHENING IT. MEANWHILE...THE EURO TAKES IT ACROSS CENTRAL
INDIANA AND NOT AS TIGHTLY WRAPPED. FOR NOW...WILL STICK WITH
INITIALIZATION WHICH SEEMS TO BE FAVORING THE GFS A TAD BY
INDICATING LIKELY POPS ACROSS THE SOUTHEAST PORTIONS OF CENTRAL
INDIANA ON TUESDAY.
PRECIP WILL DIMINISH FROM WEST TO EAST ON TUESDAY NIGHT/WEDNESDAY
MORNING WITH ALL PRECIP OUT OF THE AREA BY WEDNESDAY AFTERNOON.
THAT/S WHEN A LARGE RIDGE WILL MOVE INTO CENTRAL INDIANA BRINGING
DRY WEATHER FOR THE REMAINDER OF THE LONG TERM PERIOD. TEMPS WILL
BE SLIGHTLY BELOW NORMAL AT FIRST...BUT WARM UP BY THE END OF THE
EXTENDED PERIOD. INITIALIZATION NUMBERS LOOK REASONABLE...SO WILL
NOT DEVIATE.
&&
.AVIATION /DISCUSSION FOR THE 020000Z TAFS/...
ISSUED AT 531 PM EST FRI MAR 1 2013
WEAK SURFACE TROUGH CURRENTLY PUSHING SOUTH THROUGH THE SOUTHERN
SECTIONS OF THE FORECAST AREA. AREAS OF IFR CEILINGS/VISIBILITIES IN
LIGHT SNOW/DRIZZLE ASSOCIATED WITH THIS FEATURE..SO EXPECTING THESE
CONDITIONS TO AFFECT KHUF/KBMG THROUGH ABOUT 020200Z.
OTHERWISE...LARGE AREA OF MVFR CEILINGS AROUND 020 ACROSS THE OHIO
VALLEY EXPECTED TO LINGER TONIGHT UNDER AN INVERSION BELOW 035-040.
SURFACE WINDS GENERALLY UNDER 10 KTS AT THE TAF SITES THROUGH
021200Z.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...SMF
NEAR TERM...SMF
SHORT TERM...SMF
LONG TERM....TDUD
AVIATION...JAS
AREA FORECAST DISCUSSION
NWS INDIANAPOLIS IN
325 PM EST FRI MAR 1 2013
.UPDATE...
THE AVIATION SECTION HAS BEEN UPDATED BELOW.
&&
.SYNOPSIS...
ISSUED AT 257 PM EST FRI MAR 1 2013
ONE LAST DISTURBANCE SLIDING AROUND THE PERIPHERY OF THE LARGE UPPER
LOW TO THE NORTHEAST WILL PUSH THROUGH THE REGION EARLY THIS
EVENING...WITH CONTINUED POTENTIAL FOR LIGHT SNOW SHOWERS OR
FLURRIES IN PORTIONS OF THE SOUTHERN FORECAST AREA. HIGH PRESSURE AT
THE SURFACE WILL RETURN DRY WEATHER TO THE AREA THROUGH THE WEEKEND.
ANOTHER DISTURBANCE IN NORTHWEST FLOW ALOFT MAY PUSH THROUGH THE
AREA EARLY NEXT WEEK...MONDAY NIGHT THROUGH TUESDAY NIGHT WITH
ADDITIONAL PRECIPITATION CHANCES ASSOCIATED WITH IT. HIGH
PRESSURE...DRY WEATHER AND WARMER TEMPERATURES ARE IN STORE FOR THE
END OF NEXT WEEK.
&&
.NEAR TERM /TONIGHT/...
ISSUED AT 257 PM EST FRI MAR 1 2013
PER LATEST RADAR MOSAIC TRENDS AND MOST RECENT HRRR RUN DEPICT SNOW
SHOWERS/FLURRIES AND EVEN SOME DRIZZLE ACROSS THE SOUTH WILL BE A
LITTLE SLOWER IN EXITING THE FORECAST AREA. LEFT IN LOW CHANCES FOR
PRECIP ACROSS THE SOUTH FOR THIS EVENING...THEN WENT DRY FOR THE
OVERNIGHT. BASED ON PERSISTENCE AND THE FACT THAT CLOUDS AND EVEN TO
SOME EXTENT SOME PRECIPITATION WILL HANG AROUND A WHILE
LONGER...BUMPED UP OVERNIGHT LOWS ABOUT 5 DEGREES ABOVE MOS WHICH
YIELDS LOWS IN THE MID TO UPPER 20S.
&&
.SHORT TERM /SATURDAY THROUGH MONDAY/...
ISSUED AT 257 PM EST FRI MAR 1 2013
IT/S LOOKING LIKE A DRY WEEKEND. SURFACE HIGH PRESSURE WILL BUILD
OVER THE AREA AND REMAIN THE DOMINANT WEATHER FIXTURE FOR THE
WEEKEND. MOSTLY CLOUDY SKIES APPEAR TO LINGER OVER CENTRAL INDIANA
FOR THE FIRST HALF OF THE WEEKEND BUT THE COLUMN FINALLY BEGINS TO
DRY OUT BY SUNDAY...ALLOWING MOSTLY SUNNY TO PARTLY CLOUDY SKIES TO
RETURN TO THE AREA. NORTHERLY FLOW WILL KEEP TEMPERATURE BELOW
NORMAL THROUGH THE WEEKEND. NEXT SYSTEM TO IMPACT THE REGION COME
SOMETIME MONDAY OR MONDAY NIGHT. THERE A STARK DIFFERENCE WITH
RESPECT TO TIMING...WITH THE GFS BEING QUITE A FAST AND PROGRESSIVE
OUTLIER...SO LEANED TOWARD THE REST OF THE SLOWER GUIDANCE AND ONLY
INTRODUCED LOW CHANCE POPS LATE IN THE DAY MONDAY.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
ISSUED AT 257 PM EST FRI MAR 1 2013
THE EXTENDED PERIOD WILL START OUT RATHER ACTIVE AS A SURFACE LOW
FROM THE SOUTHERN PLAINS EVENTUALLY MERGES WITH AN UPPER LEVEL LOW
COMING OUT OF THE NORTHERN PLAINS ON TUESDAY. THE SURFACE LOW WILL
REACH CENTRAL INDIANA FIRST THOUGH BRINGING RAIN AND SNOW CHANCES ON
MONDAY. THE GFS AND EURO CONTINUE TO DIFFER ON TRACK OF UPPER LEVEL
LOW WITH THE GFS DIGGING IT FURTHER INTO THE TENNESSEE VALLEY WHILE
STRENGTHENING IT. MEANWHILE...THE EURO TAKES IT ACROSS CENTRAL
INDIANA AND NOT AS TIGHTLY WRAPPED. FOR NOW...WILL STICK WITH
INITIALIZATION WHICH SEEMS TO BE FAVORING THE GFS A TAD BY
INDICATING LIKELY POPS ACROSS THE SOUTHEAST PORTIONS OF CENTRAL
INDIANA ON TUESDAY.
PRECIP WILL DIMINISH FROM WEST TO EAST ON TUESDAY NIGHT/WEDNESDAY
MORNING WITH ALL PRECIP OUT OF THE AREA BY WEDNESDAY AFTERNOON.
THAT/S WHEN A LARGE RIDGE WILL MOVE INTO CENTRAL INDIANA BRINGING
DRY WEATHER FOR THE REMAINDER OF THE LONG TERM PERIOD. TEMPS WILL
BE SLIGHTLY BELOW NORMAL AT FIRST...BUT WARM UP BY THE END OF THE
EXTENDED PERIOD. INITIALIZATION NUMBERS LOOK REASONABLE...SO WILL
NOT DEVIATE.
&&
.AVIATION /DISCUSSION FOR THE 012100Z TAF UPDATE/...
ISSUED AT 325 PM EST FRI MAR 1 2013
NO SIGNIFICANT CHANGES MADE TO KIND TAF. SOME LIGHT SNOW AND DRIZZLE
WILL CONTINUE AT KIND FOR PERHAPS A COUPLE MORE HOURS...BUT NOT
EXPECTING ANY ADDITIONAL VISIBILITY RESTRICTIONS. CEILINGS SHOULD
GRADUALLY LIFT TO AT OR ABOVE BKN020 BY 23Z OR SO.
PREVIOUS DISCUSSION FOLLOWS...
BRIEF IFR CONDITIONS AT A FEW ISOLATED TAF SITES IS EXPECTED TO
IMPROVE TO MVFR THIS AFTERNOON FOR THE REST OF THE TAF PERIOD.
BROAD CYCLONIC FLOW IS EXPECTED TO PERSIST THE NEXT 24 HOURS AS
STRONG RIDGING ALOFT REMAINS TO THE WEST AND A DEEP TROUGH REMAINS
OVER THE EASTERN UNITED STATES. TIME HEIGHT SECTIONS CONTINUE TO
SHOW SATURATED LOWER LEVELS THROUGH SATURDAY...WITH CCL GENERALLY
LESS THAN 3000 FT. THUS MVFR CIGS ARE EXPECTED THROUGH MUCH OF THE
PERIOD WITH NORTH WINDS OF 5 TO 10 MPH.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...SMF
NEAR TERM...SMF
SHORT TERM...SMF
LONG TERM....TDUD
AVIATION...JP/50
AREA FORECAST DISCUSSION
NWS INDIANAPOLIS IN
259 PM EST FRI MAR 1 2013
.UPDATE...
THE SYNOPSIS...NEAR TERM...SHORT TERM AND LONG TERM SECTIONS HAVE
BEEN UPDATED BELOW.
&&
.SYNOPSIS...
ISSUED AT 257 PM EST FRI MAR 1 2013
ONE LAST DISTURBANCE SLIDING AROUND THE PERIPHERY OF THE LARGE UPPER
LOW TO THE NORTHEAST WILL PUSH THROUGH THE REGION EARLY THIS
EVENING...WITH CONTINUED POTENTIAL FOR LIGHT SNOW SHOWERS OR
FLURRIES IN PORTIONS OF THE SOUTHERN FORECAST AREA. HIGH PRESSURE AT
THE SURFACE WILL RETURN DRY WEATHER TO THE AREA THROUGH THE WEEKEND.
ANOTHER DISTURBANCE IN NORTHWEST FLOW ALOFT MAY PUSH THROUGH THE
AREA EARLY NEXT WEEK...MONDAY NIGHT THROUGH TUESDAY NIGHT WITH
ADDITIONAL PRECIPITATION CHANCES ASSOCIATED WITH IT. HIGH
PRESSURE...DRY WEATHER AND WARMER TEMPERATURES ARE IN STORE FOR THE
END OF NEXT WEEK.
&&
.NEAR TERM /TONIGHT/...
ISSUED AT 257 PM EST FRI MAR 1 2013
PER LATEST RADAR MOSAIC TRENDS AND MOST RECENT HRRR RUN DEPICT SNOW
SHOWERS/FLURRIES AND EVEN SOME DRIZZLE ACROSS THE SOUTH WILL BE A
LITTLE SLOWER IN EXITING THE FORECAST AREA. LEFT IN LOW CHANCES FOR
PRECIP ACROSS THE SOUTH FOR THIS EVENING...THEN WENT DRY FOR THE
OVERNIGHT. BASED ON PERSISTENCE AND THE FACT THAT CLOUDS AND EVEN TO
SOME EXTENT SOME PRECIPITATION WILL HANG AROUND A WHILE
LONGER...BUMPED UP OVERNIGHT LOWS ABOUT 5 DEGREES ABOVE MOS WHICH
YIELDS LOWS IN THE MID TO UPPER 20S.
&&
.SHORT TERM /SATURDAY THROUGH MONDAY/...
ISSUED AT 257 PM EST FRI MAR 1 2013
IT/S LOOKING LIKE A DRY WEEKEND. SURFACE HIGH PRESSURE WILL BUILD
OVER THE AREA AND REMAIN THE DOMINANT WEATHER FIXTURE FOR THE
WEEKEND. MOSTLY CLOUDY SKIES APPEAR TO LINGER OVER CENTRAL INDIANA
FOR THE FIRST HALF OF THE WEEKEND BUT THE COLUMN FINALLY BEGINS TO
DRY OUT BY SUNDAY...ALLOWING MOSTLY SUNNY TO PARTLY CLOUDY SKIES TO
RETURN TO THE AREA. NORTHERLY FLOW WILL KEEP TEMPERATURE BELOW
NORMAL THROUGH THE WEEKEND. NEXT SYSTEM TO IMPACT THE REGION COME
SOMETIME MONDAY OR MONDAY NIGHT. THERE A STARK DIFFERENCE WITH
RESPECT TO TIMING...WITH THE GFS BEING QUITE A FAST AND PROGRESSIVE
OUTLIER...SO LEANED TOWARD THE REST OF THE SLOWER GUIDANCE AND ONLY
INTRODUCED LOW CHANCE POPS LATE IN THE DAY MONDAY.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
ISSUED AT 257 PM EST FRI MAR 1 2013
THE EXTENDED PERIOD WILL START OUT RATHER ACTIVE AS A SURFACE LOW
FROM THE SOUTHERN PLAINS EVENTUALLY MERGES WITH AN UPPER LEVEL LOW
COMING OUT OF THE NORTHERN PLAINS ON TUESDAY. THE SURFACE LOW WILL
REACH CENTRAL INDIANA FIRST THOUGH BRINGING RAIN AND SNOW CHANCES ON
MONDAY. THE GFS AND EURO CONTINUE TO DIFFER ON TRACK OF UPPER LEVEL
LOW WITH THE GFS DIGGING IT FURTHER INTO THE TENNESSEE VALLEY WHILE
STRENGTHENING IT. MEANWHILE...THE EURO TAKES IT ACROSS CENTRAL
INDIANA AND NOT AS TIGHTLY WRAPPED. FOR NOW...WILL STICK WITH
INITIALIZATION WHICH SEEMS TO BE FAVORING THE GFS A TAD BY
INDICATING LIKELY POPS ACROSS THE SOUTHEAST PORTIONS OF CENTRAL
INDIANA ON TUESDAY.
PRECIP WILL DIMINISH FROM WEST TO EAST ON TUESDAY NIGHT/WEDNESDAY
MORNING WITH ALL PRECIP OUT OF THE AREA BY WEDNESDAY AFTERNOON.
THAT/S WHEN A LARGE RIDGE WILL MOVE INTO CENTRAL INDIANA BRINGING
DRY WEATHER FOR THE REMAINDER OF THE LONG TERM PERIOD. TEMPS WILL
BE SLIGHTLY BELOW NORMAL AT FIRST...BUT WARM UP BY THE END OF THE
EXTENDED PERIOD. INITIALIZATION NUMBERS LOOK REASONABLE...SO WILL
NOT DEVIATE.
&&
.AVIATION /DISCUSSION FOR THE 011800Z TAFS/...
ISSUED AT 1118 AM EST FRI MAR 1 2013
BRIEF IFR CONDITIONS AT A FEW ISOLATED TAF SITES IS EXPECTED TO
IMPROVE TO MVFR THIS AFTERNOON FOR THE REST OF THE TAF PERIOD.
BROAD CYCLONIC FLOW IS EXPECTED TO PERSIST THE NEXT 24 HOURS AS
STRONG RIDGING ALOFT REMAINS TO THE WEST AND A DEEP TROUGH REMAINS
OVER THE EASTERN UNITED STATES. TIME HEIGHT SECTIONS CONTINUE TO
SHOW SATURATED LOWER LEVELS THROUGH SATURDAY...WITH CCL GENERALLY
LESS THAN 3000 FT. THUS MVFR CIGS ARE EXPECTED THROUGH MUCH OF THE
PERIOD WITH NORTH WINDS OF 5 TO 10 MPH.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...SMF
NEAR TERM...SMF
SHORT TERM...SMF
LONG TERM....TDUD
AVIATION...JP
AREA FORECAST DISCUSSION...CORRECTED
NWS NORTHERN INDIANA
100 PM EST FRI MAR 1 2013
.AVIATION... /18 UTC TAFS/
SLIGHT IMPROVEMENT WRT FLIGHT CONDS THIS AFTN WITH INCRSD
MIXING/DEPTH OF BLYR. ANTICIPATE CONTD ALBEIT SLIGHT ERORSIVE
DOWNWARD VERTICAL MOTION TO MAINTAIN PRIMARILY VFR CONDS OVERNIGHT.
SLIGHT INCR IN MSTR PER BACKING WIND FLOW ACRS LK MI ON SAT MAY
AFFORD HIR END MVFR CIGS ACRS NRN IN WITH SCT FLURRIES/SPCLY INVOF
KSBN.
&&
.PREV DISCUSSION... /ISSUED 444 AM EST FRI MAR 1 2013/
SHORT TERM...TODAY THROUGH SATURDAY NIGHT
RELATIVELY QUIET PERIOD IN STORE FOR THE UPCOMING WEEKEND WITH MAIN
SHORT TERM FOCUS ON LINGERING LIGHT PRECIP THIS MORNING...AND
TEMPERATURE TRENDS.
WATER VAPOR IMAGERY/07Z RAP ANALYSIS SUGGEST WEAK UPPER VORT MAX
DROPPING SOUTHWARD ACROSS NORTHERN INDIANA THIS MORNING. HAVE NOTED
SOME UPSWING OVER PAST HOUR ACROSS CENTRAL/SOUTHERN SECTIONS OF
FORECAST AREA OF SOME -FZDZ PER RADAR/SFC OBSERVATIONS BUT FZDZ IS
EXPECTED TO REMAIN LIGHT ENOUGH TO PREVENT SIGNIFICANT IMPACTS THIS
MORNING. WITH AXIS OF WEAK DPVA SHIFTING ACROSS SOUTHERN/CENTRAL
AREAS WILL CONFINE EARLY MORNING FZDZ MENTION TO THESE LOCATIONS
WITH MAINLY DRY CONDITIONS ACROSS THE NORTH WERE LOW LEVEL DRY AIR
ADVECTION HAS BECOME MORE PRONOUNCED IN THE WAKE OF ASSOCIATED WEAK
INVERTED SFC TROUGH FEATURE. MARINE OBS SUGGEST SOME AUGMENTATION TO
SYNOPTIC CONVERGENCE ASSOCIATED WITH THIS TROUGH WITH WEAK LAKE
INDUCED THERMAL TROUGHING. THIS MAY ACT TO PERPETUATE SOME FLURRIES
ACROSS EXTREME NORTHWEST SECTIONS OF THE FORECAST AREA
TODAY...ALTHOUGH INCREASINGLY DRY LOW LEVEL AIR MASS SHOULD LIMIT
FLURRY/LIGHT SNOW SHOWER ACTIVITY. LIMITED DIURNAL MOVEMENT IN
TEMPERATURES EXPECTED AGAIN TODAY WITH RELATIVELY WEAK THERMAL
ADVECTION AND PERSISTENCE OF LOW CLOUD DECK.
FOR TONIGHT INTO SATURDAY...LONGWAVE RIDING ACROSS WESTERN CONUS
WILL BEGIN TO SHIFT EASTWARD AS WEAK UPPER PV ANOMALY ACROSS
NORTHERN PLAINS ADVANCES INTO THE WESTERN GREAT LAKES REGION. UPPER
FORCING/DYNAMICS LOOK TO BE QUITE WEAK WITH THIS SHORT WAVE HOWEVER
AS PV ANOMALY BECOMES AFFECTED BY MID/UPPER LEVEL DEFORMATION FLOW
ACROSS GREAT LAKES REGION. PASSAGE OF THIS FEATURE MAY MARK A SUBTLE
UPSWING IN WEAK LAKE RESPONSE IN THE FORM OF SCT FLURRIES/LIGHT SNOW
SHOWERS SATURDAY/SATURDAY NIGHT. LAKE EFFECT PARAMETERS QUITE MEAGER
HOWEVER WITH VERY DRY MID LEVEL AIR IN PLACE...AND MARGINAL LAKE/850
HPA DELTA TEMPS. DESPITE SOME WEAK REINFORCING LOW LEVEL CAA WITH
AFOREMENTIONED NORTHERN PLAINS SHORT WAVE SATURDAY...HIGH TEMPS
SHOULD BE SIMILAR TO THAT OF FRIDAY WITH THE POSSIBILITY OF A BIT
MORE INSOLATION OFFSETTING SLIGHTLY COOLER LOW LEVEL THERMAL
PROFILES.
&&
LONG TERM...
SUNDAY THROUGH THURSDAY...THE MAIN CHALLENGE THIS PERIOD IS THE
TIMING AND TRACK OF A SHORT WAVE THAT WILL TOP THE UPSTREAM RIDGE
AND MOVE INTO THE MIDWEST NEXT WEEK. THE ECMWF APPEARS TO HAVE
INITIALIZED THIS SYSTEM REASONABLY WELL AND HAS ALSO SHOWN SOME RUN
TO RUN CONSISTENCY. FOR THIS PACKAGE...BLENDED SEVERAL MODELS
INCLUDING THE ECMWF OPERATIONAL RUN...EC ENSEMBLE MEAN...AND GFS
OPERATIONAL RUN WITH ENSEMBLE MEMBERS. GIVEN THE HIGH LATITUDE
STRONG POSITIVE ANOMALY...CONCERN THAT THESE MODELS MAY BE TOO FAST
WITH THIS SYSTEM. THE ECMWF HAS TRENDED SLIGHTLY SLOWER WITH THIS
SYSTEM WITH AN ARRIVAL TIME OF TUESDAY/TUESDAY NIGHT. HAVE TRENDED
THE SNOW CHANCES HIGHER THESE PERIODS...BUT KEPT IN CHANCE CATEGORY
DUE TO A LARGE GFS ENSEMBLE SPREAD AND LARGE NORMALIZED STANDARD
DEVIATIONS AMONG ECMWF ENSEMBLE MEMBERS. A WEAK LAKE RESPONSE IS
EXPECTED AFTER THIS SYSTEM PASSES...BUT DELTA T VALUES SHOULD REMAIN
LESS THAN 10. OTHERWISE...KEPT TEMPERATURES COLD THROUGH WEDNESDAY.
TEMPS SHOULD RISE ABOVE NORMAL THURSDAY AS AN UPPER LEVEL RIDGE
BUILDS OVER THE REGION. GFS MEAN ENSEMBLE MEX MOS TEMPS APPEAR ON
TRACK.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 5 AM EST SUNDAY FOR LMZ043-046.
&&
$$
SHORT TERM...MARSILI
LONG TERM...SKIPPER
AVIATION...MURPHY
CORRECTED ISSUANCE TIME
AREA FORECAST DISCUSSION
NWS NORTHERN INDIANA
6100 PM EST FRI MAR 1 2013
.AVIATION... /18 UTC TAFS/
SLIGHT IMPROVEMENT WRT FLIGHT CONDS THIS AFTN WITH INCRSD
MIXING/DEPTH OF BLYR. ANTICIPATE CONTD ALBEIT SLIGHT ERORSIVE
DOWNWARD VERTICAL MOTION TO MAINTAIN PRIMARILY VFR CONDS OVERNIGHT.
SLIGHT INCR IN MSTR PER BACKING WIND FLOW ACRS LK MI ON SAT MAY
AFFORD HIR END MVFR CIGS ACRS NRN IN WITH SCT FLURRIES/SPCLY INVOF
KSBN.
&&
.PREV DISCUSSION... /ISSUED 444 AM EST FRI MAR 1 2013/
SHORT TERM...TODAY THROUGH SATURDAY NIGHT
RELATIVELY QUIET PERIOD IN STORE FOR THE UPCOMING WEEKEND WITH MAIN
SHORT TERM FOCUS ON LINGERING LIGHT PRECIP THIS MORNING...AND
TEMPERATURE TRENDS.
WATER VAPOR IMAGERY/07Z RAP ANALYSIS SUGGEST WEAK UPPER VORT MAX
DROPPING SOUTHWARD ACROSS NORTHERN INDIANA THIS MORNING. HAVE NOTED
SOME UPSWING OVER PAST HOUR ACROSS CENTRAL/SOUTHERN SECTIONS OF
FORECAST AREA OF SOME -FZDZ PER RADAR/SFC OBSERVATIONS BUT FZDZ IS
EXPECTED TO REMAIN LIGHT ENOUGH TO PREVENT SIGNIFICANT IMPACTS THIS
MORNING. WITH AXIS OF WEAK DPVA SHIFTING ACROSS SOUTHERN/CENTRAL
AREAS WILL CONFINE EARLY MORNING FZDZ MENTION TO THESE LOCATIONS
WITH MAINLY DRY CONDITIONS ACROSS THE NORTH WERE LOW LEVEL DRY AIR
ADVECTION HAS BECOME MORE PRONOUNCED IN THE WAKE OF ASSOCIATED WEAK
INVERTED SFC TROUGH FEATURE. MARINE OBS SUGGEST SOME AUGMENTATION TO
SYNOPTIC CONVERGENCE ASSOCIATED WITH THIS TROUGH WITH WEAK LAKE
INDUCED THERMAL TROUGHING. THIS MAY ACT TO PERPETUATE SOME FLURRIES
ACROSS EXTREME NORTHWEST SECTIONS OF THE FORECAST AREA
TODAY...ALTHOUGH INCREASINGLY DRY LOW LEVEL AIR MASS SHOULD LIMIT
FLURRY/LIGHT SNOW SHOWER ACTIVITY. LIMITED DIURNAL MOVEMENT IN
TEMPERATURES EXPECTED AGAIN TODAY WITH RELATIVELY WEAK THERMAL
ADVECTION AND PERSISTENCE OF LOW CLOUD DECK.
FOR TONIGHT INTO SATURDAY...LONGWAVE RIDING ACROSS WESTERN CONUS
WILL BEGIN TO SHIFT EASTWARD AS WEAK UPPER PV ANOMALY ACROSS
NORTHERN PLAINS ADVANCES INTO THE WESTERN GREAT LAKES REGION. UPPER
FORCING/DYNAMICS LOOK TO BE QUITE WEAK WITH THIS SHORT WAVE HOWEVER
AS PV ANOMALY BECOMES AFFECTED BY MID/UPPER LEVEL DEFORMATION FLOW
ACROSS GREAT LAKES REGION. PASSAGE OF THIS FEATURE MAY MARK A SUBTLE
UPSWING IN WEAK LAKE RESPONSE IN THE FORM OF SCT FLURRIES/LIGHT SNOW
SHOWERS SATURDAY/SATURDAY NIGHT. LAKE EFFECT PARAMETERS QUITE MEAGER
HOWEVER WITH VERY DRY MID LEVEL AIR IN PLACE...AND MARGINAL LAKE/850
HPA DELTA TEMPS. DESPITE SOME WEAK REINFORCING LOW LEVEL CAA WITH
AFOREMENTIONED NORTHERN PLAINS SHORT WAVE SATURDAY...HIGH TEMPS
SHOULD BE SIMILAR TO THAT OF FRIDAY WITH THE POSSIBILITY OF A BIT
MORE INSOLATION OFFSETTING SLIGHTLY COOLER LOW LEVEL THERMAL
PROFILES.
&&
LONG TERM...
SUNDAY THROUGH THURSDAY...THE MAIN CHALLENGE THIS PERIOD IS THE
TIMING AND TRACK OF A SHORT WAVE THAT WILL TOP THE UPSTREAM RIDGE
AND MOVE INTO THE MIDWEST NEXT WEEK. THE ECMWF APPEARS TO HAVE
INITIALIZED THIS SYSTEM REASONABLY WELL AND HAS ALSO SHOWN SOME RUN
TO RUN CONSISTENCY. FOR THIS PACKAGE...BLENDED SEVERAL MODELS
INCLUDING THE ECMWF OPERATIONAL RUN...EC ENSEMBLE MEAN...AND GFS
OPERATIONAL RUN WITH ENSEMBLE MEMBERS. GIVEN THE HIGH LATITUDE
STRONG POSITIVE ANOMALY...CONCERN THAT THESE MODELS MAY BE TOO FAST
WITH THIS SYSTEM. THE ECMWF HAS TRENDED SLIGHTLY SLOWER WITH THIS
SYSTEM WITH AN ARRIVAL TIME OF TUESDAY/TUESDAY NIGHT. HAVE TRENDED
THE SNOW CHANCES HIGHER THESE PERIODS...BUT KEPT IN CHANCE CATEGORY
DUE TO A LARGE GFS ENSEMBLE SPREAD AND LARGE NORMALIZED STANDARD
DEVIATIONS AMONG ECMWF ENSEMBLE MEMBERS. A WEAK LAKE RESPONSE IS
EXPECTED AFTER THIS SYSTEM PASSES...BUT DELTA T VALUES SHOULD REMAIN
LESS THAN 10. OTHERWISE...KEPT TEMPERATURES COLD THROUGH WEDNESDAY.
TEMPS SHOULD RISE ABOVE NORMAL THURSDAY AS AN UPPER LEVEL RIDGE
BUILDS OVER THE REGION. GFS MEAN ENSEMBLE MEX MOS TEMPS APPEAR ON
TRACK.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 5 AM EST SUNDAY FOR LMZ043-046.
&&
$$
SHORT TERM...MARSILI
LONG TERM...SKIPPER
AVIATION...MURPHY
AREA FORECAST DISCUSSION
NWS LOUISVILLE KY
1254 PM EST FRI MAR 01 2013
...Updated Aviation Discussion...
.Forecast Update...
Issued at 1150 AM EST Fri Mar 1 2013
Did a quick update to adjust temps/POPs to current observations.
Also increased POPs after 21Z and through the evening hours to
likely as latest RAP model indicates some enhanced light to moderate
bands of precip developing by late afternoon or early evening.
Temps should be warm enough for an initial rain/snow mix changing
over to all snow this evening. With temps still above freezing,
think that impacts for the evening rush hour will be minimal but
will continue to monitor.
&&
.Short Term (Now - Saturday)...
Issued at 300 AM EST Fri Mar 1 2013
Broad upper trough is over the Midwest, with a quasi-stationary
center over southern Illinois. This feature is allowing some light
snow to fall over western Kentucky and southwest Indiana. Some
deeper moisture moving into south central Kentucky should still
allow additional snows to develop across the rest of that region
through daybreak. However, this snow looks light, as only a few
sites are reporting more than a trace of precip. Model soundings
indicate that the top of the saturated is right around -10C, so
there is not much room for prime dendritic growth. Thus not
expecting more than a light dusting the rest of the morning. Will
monitor webcams and radar through the day to see if any special
products need to be issued.
Later this afternoon, the upper low center should have drifted into
south central Kentucky. This shift should change the focus for
precip more to the south as well, with a sharp gradient in
precipitation from north to south across the forecast area.
Temperatures should warm into the upper 30s for most locations,
which would bring more of a light rain/snow mix and no further
accumulations. It should be noted that guidance tries to bring
temperatures into the 40s today, but continue to undercut that
guidance due to cloud cover and precipitation.
Tonight the upper low wobbles south into eastern Tennessee, which
should continue to drag the best precip chances southward. We should
switch back to all snow by sunset, bringing another light dusting
across the southern half of the forecast area, a half inch or less.
Will keep only a slight chance for further snow during the day
Saturday across the KY/TN border, as the upper low center weakens
and accelerates eastward. A strengthening north wind and continued
cloud cover will bring temperatures likely a couple of degrees
cooler than today, making for a raw Saturday.
.Long Term (Saturday Night through Thursday)...
Issued at 320 AM EST Fri Mar 01 2013
The beginning of the long term period will feature a broad trough
across the eastern CONUS, with an expansive ridge across the Rocky
Mountains. The flow will flatten and become more progressive by
early next week, as a strong shortwave drops through the Northern
Plains and into the Ohio Valley. In the wake of the disturbance, an
upper ridge will build in for the end of the long term period.
Surface high pressure will slip into the Ohio Valley during the day
on Sunday, which may finally allow for a few peaks of sunshine and
an end to the gloomy weather pattern we`ve been stuck in! However,
this high will quickly slide east by early Monday as the next system
takes aim on the region.
Quite a bit of uncertainty still exists for the strong system set to
impact the region Monday night into Tuesday. Guidance is really
struggling with the placement of the synoptic wave, which has large
implications on surface features and thermodynamic profiles.
Interestingly, the NAO index has been largely overforecasted
(forecasted to be much more negative than it actually is) by MRF
ensemble guidance the past several days. This could have
implications on the track of this approaching wave, as the
persistent east coast trough may break down a bit quicker than
guidance has advertised, which would suggest a more northern track
and less snow potential.
To break down the guidance, it looks as if the 01/00Z GFS is the
furthest south with the synoptic wave. Oddly enough though, it has
warmer low-level thermal profiles than the 01/00Z ECMWF. The 01/00Z
ECMWF is much more bullish in the strength of the shortwave trough,
so despite it`s more northern track, it wraps cooler air into the
system which keeps surface temperatures cooler. The 01/00Z GEM has
a similar track to the 01/00Z ECMWF, but is warmer with its thermal
profiles. Have decided to trend a bit warmer with this forecast
package, favoring the 01/00Z GEM northern track and warmer
profiles. There will most likely be some flakes mixed in,
especially across southern Indiana and north central Kentucky, but
at this point am not all too impressed with significant accumulation
chances. Obviously, still plenty of time to iron out the specific
details, so stay tuned to upcoming forecasts as things could
certainly change.
Otherwise, the shortwave quickly passes through the region, with
upper level ridging building into the Ohio Valley in its wake on
Wednesday. For you spring lovers (me included!), it looks like
things will finally warm up by the end of next week to near normal
values, with highs approaching 50 degrees on Thursday.
&&
.Aviation (18Z TAF Issuance)...
Issued at 1250 PM EST Fri Mar 1 2013
An upper level trough slowly sagging south through the area will
continue to provide light precip throughout the TAF period. For the
rest of this afternoon, expect light on and off -RASN. By late this
afternoon/early evening, short range high res models indicate an
increase in banded precip activity. While this might be -RASN at
onset, it is expected to transition to all snow this evening with
light brief accumulations possible. With sfc temps remaining above
freezing this evening, don`t expect it to cause slick spots on
runways but do expect reduced vsbys/cigs to IFR conditions.
Although most of the widespread snow shower activity should decline
after 3-4Z, flight conditions will likely stay in the IFR cat due to
cigs through much of the night. A sfc trough is expected to move
south through the area tonight shifting winds from NW to N and
causing flight conditions to improve to MVFR. This looks to happen
around 9Z at SDF/LEX and 13Z at BWG respectively.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
KY...NONE.
$$
Update...........AMS
Short Term.......RJS
Long Term........KD
Aviation.........AMS
AREA FORECAST DISCUSSION
NWS LOUISVILLE KY
1150 AM EST FRI MAR 01 2013
.Forecast Update...
Issued at 1150 AM EST Fri Mar 1 2013
Did a quick update to adjust temps/POPs to current observations.
Also increased POPs after 21Z and through the evening hours to
likely as latest RAP model indicates some enhanced light to moderate
bands of precip developing by late afternoon or early evening.
Temps should be warm enough for an initial rain/snow mix changing
over to all snow this evening. With temps still above freezing,
think that impacts for the evening rush hour will be minimal but
will continue to monitor.
&&
.Short Term (Now - Saturday)...
Issued at 300 AM EST Fri Mar 1 2013
Broad upper trough is over the Midwest, with a quasi-stationary
center over southern Illinois. This feature is allowing some light
snow to fall over western Kentucky and southwest Indiana. Some
deeper moisture moving into south central Kentucky should still
allow additional snows to develop across the rest of that region
through daybreak. However, this snow looks light, as only a few
sites are reporting more than a trace of precip. Model soundings
indicate that the top of the saturated is right around -10C, so
there is not much room for prime dendritic growth. Thus not
expecting more than a light dusting the rest of the morning. Will
monitor webcams and radar through the day to see if any special
products need to be issued.
Later this afternoon, the upper low center should have drifted into
south central Kentucky. This shift should change the focus for
precip more to the south as well, with a sharp gradient in
precipitation from north to south across the forecast area.
Temperatures should warm into the upper 30s for most locations,
which would bring more of a light rain/snow mix and no further
accumulations. It should be noted that guidance tries to bring
temperatures into the 40s today, but continue to undercut that
guidance due to cloud cover and precipitation.
Tonight the upper low wobbles south into eastern Tennessee, which
should continue to drag the best precip chances southward. We should
switch back to all snow by sunset, bringing another light dusting
across the southern half of the forecast area, a half inch or less.
Will keep only a slight chance for further snow during the day
Saturday across the KY/TN border, as the upper low center weakens
and accelerates eastward. A strengthening north wind and continued
cloud cover will bring temperatures likely a couple of degrees
cooler than today, making for a raw Saturday.
.Long Term (Saturday Night through Thursday)...
Issued at 320 AM EST Fri Mar 01 2013
The beginning of the long term period will feature a broad trough
across the eastern CONUS, with an expansive ridge across the Rocky
Mountains. The flow will flatten and become more progressive by
early next week, as a strong shortwave drops through the Northern
Plains and into the Ohio Valley. In the wake of the disturbance, an
upper ridge will build in for the end of the long term period.
Surface high pressure will slip into the Ohio Valley during the day
on Sunday, which may finally allow for a few peaks of sunshine and
an end to the gloomy weather pattern we`ve been stuck in! However,
this high will quickly slide east by early Monday as the next system
takes aim on the region.
Quite a bit of uncertainty still exists for the strong system set to
impact the region Monday night into Tuesday. Guidance is really
struggling with the placement of the synoptic wave, which has large
implications on surface features and thermodynamic profiles.
Interestingly, the NAO index has been largely overforecasted
(forecasted to be much more negative than it actually is) by MRF
ensemble guidance the past several days. This could have
implications on the track of this approaching wave, as the
persistent east coast trough may break down a bit quicker than
guidance has advertised, which would suggest a more northern track
and less snow potential.
To break down the guidance, it looks as if the 01/00Z GFS is the
furthest south with the synoptic wave. Oddly enough though, it has
warmer low-level thermal profiles than the 01/00Z ECMWF. The 01/00Z
ECMWF is much more bullish in the strength of the shortwave trough,
so despite it`s more northern track, it wraps cooler air into the
system which keeps surface temperatures cooler. The 01/00Z GEM has
a similar track to the 01/00Z ECMWF, but is warmer with its thermal
profiles. Have decided to trend a bit warmer with this forecast
package, favoring the 01/00Z GEM northern track and warmer
profiles. There will most likely be some flakes mixed in,
especially across southern Indiana and north central Kentucky, but
at this point am not all too impressed with significant accumulation
chances. Obviously, still plenty of time to iron out the specific
details, so stay tuned to upcoming forecasts as things could
certainly change.
Otherwise, the shortwave quickly passes through the region, with
upper level ridging building into the Ohio Valley in its wake on
Wednesday. For you spring lovers (me included!), it looks like
things will finally warm up by the end of next week to near normal
values, with highs approaching 50 degrees on Thursday.
&&
.Aviation (12Z TAF Issuance)...
Issued at 610 AM EST Fri Mar 1 2013
Upper level low has drifted into western Kentucky early this
morning, and this low will continue drifting east through the day.
An east-west oriented band of mid/upper level clouds has developed
ahead of this feature across central Kentucky, and these clouds will
help to bring heavier snows just in between the TAF sites this
morning. Should continue to see high end IFR/low end MVFR cigs most
of the day, as the presence of the upper low should prevent
clearing. Cigs may raise a little by mid/late afternoon before
returning again to current levels this evening. The chance for snow
showers overnight should be limited to KBWG, as the upper low veers
southeast into eastern Tennessee.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
KY...NONE.
$$
Update...........AMS
Short Term.......RJS
Long Term........KD
Aviation.........RJS
AREA FORECAST DISCUSSION
NWS DULUTH MN
1116 AM CST FRI MAR 1 2013
.UPDATE...CLOUDS AND FLURRIES/SNOW SHOWERS CONTINUED ACROSS THE
HEAD OF THE LAKES AND ACROSS THE SOUTH SHORE OF LAKE SUPERIOR.
WILL LIKELY BE SOME FLURRIES/SNOW SHOWERS LINGERING INTO THE
AFTERNOON BUT CLOUDS WILL SLOWLY DECREASE THROUGHOUT THE DAY.
STILL A FAIR AMOUNT OF SUNSHINE IN THE NORTH. OTHERWISE ZONES AND
GRIDS IN GOOD SHAPE FOR THE AFTERNOON WITH LITTLE CHANGE.
&&
.PREV DISCUSSION... /ISSUED 610 AM CST FRI MAR 1 2013/
UPDATE...HAVE ADDED A MENTION OF FLURRIES TO THE HEAD OF LAKE
SUPERIOR INCLUDING THE TWIN PORTS FOR EARLY THIS MORNING. REST OF
THE FORECAST UNCHANGED.
PREV DISCUSSION... /ISSUED 544 AM CST FRI MAR 1 2013/
AVIATION...12Z TAFS
MVFR CEILINGS REMAINED FROM ABOUT KTWM INTO THE KBRD AREA...AND
COVERED ALL AREAS TO THE SOUTHEAST INCLUDING NORTHWEST WISCONSIN.
EAST NORTHEAST WINDS WILL CONTINUE TO GENERATE CLOUDS
TODAY AROUND LAKE SUPERIOR...ALTHOUGH WE DO THINK THEY WILL DISSIPATE
SOME FROM THE NORTH. DRIER AIR IS FORECAST TO MOVE OVER LAKE
SUPERIOR...AND THAT SHOULD HELP DISSIPATE SOME OF THE
CLOUDS...PARTICULARLY OVER KDLH. THE CEILINGS AT KBRD SHOULD ALSO
DIMINISH THROUGH THE DAY. THE RAP DOES SUGGEST MORE MVFR CEILINGS
MAY DEVELOP THIS AFTERNOON...SO WE INCLUDED A TEMPO GROUP AT
KBRD/KHIB. SOME FLURRIES WILL ALSO OCCUR UNDER SOME OF THESE
CLOUDS.
PREV DISCUSSION... /ISSUED 244 AM CST FRI MAR 1 2013/
SHORT TERM...LITTLE CHANGE TO THE PRESSURE PATTERN FROM 24 HOURS
AGO. THE TROF REMAINS STUCK NEAR THE RED RIVER VALLEY WITH THE
RIDGE AXIS TO THE W AND THE LARGE SFC LOW NOW OFF THE E
COAST...BUT CIRCULATION OVER THE FA REMAINS THE SAME. THE
DIFFERENCE IS CLOUD COVER WITH CI AND A FEW MID CLOUDS OVER THE MN
FA AND LOW CLOUDS OVER NW WI TO NEAR THE TWIN PORTS. THE SFC TROF
WILL EVENTUALLY BREAK DOWN TODAY AS THE SFC RIDGE MOVES E AND OVER
THE FA BY 00Z SATURDAY. WILL TAKE AWHILE FOR THE CLOUDS TO ERODE
AS THE RIDGE SLOWLY MOVES OVERHEAD. EVEN WITH THE NE FLOW
CONTINUING OVER LAKE SUPERIOR...AIR MASS IS TOO DRY FOR ANY LES TO
FORM AND HAVE REMOVED THE MENTION OF FLURRIES.
THE SFC RIDGE AXIS REMAINS NEARLY STATIONARY OVER THE FA THROUGH
SATURDAY. WITH A NLY FLOW ALOFT AND 850MB TEMPS AROUND -12C...MIN
TEMPS TONIGHT WILL DROP BELOW ZERO OVER THE NORTHERN HALF OF THE FA.
PLENTY OF SUN ON SATURDAY WILL NOT BE ENOUGH TO COUNTERACT THE COLD
AIR ALOFT AND MAX TEMPS WILL BE IN THE 20S WITH SOME SPOTS REACHING
30F.
LONG TERM...FRIDAY NIGHT THROUGH THURSDAY.
SEVERAL CONCERNS EXIST THROUGH THE PERIOD...NAMELY CHANCES FOR LAKE
EFFECT SNOW AND THE TRACK OF A STRONGER LOW PRESSURE SYSTEM THAT
COULD IMPACT THE NORTHLAND AS EARLY AS SUNDAY NIGHT...BUT MORE SO
MONDAY INTO MONDAY NIGHT.
THE MODELS ARE NOT IN REAL GOOD AGREEMENT THROUGH THE EXTENDED
PERIOD...WITH BOTH RUN TO RUN AND MODEL TO MODEL VARIABILITY.
EARLY IN THE PERIOD AN UPPER LEVEL TROUGH WILL EXTEND OVER LAKE
SUPERIOR INTO MICHIGAN...WITH THE STRONGER SHORTWAVE OVER THE
NORTHWEST CONUS/BC AREA. LOW LEVEL FLOW WILL BECOME SOUTHEAST
SATURDAY NIGHT...AND AN AREA OF LOW LEVEL WAA WILL APPROACH THE CWA
FROM THE WEST. THERE WILL BE A CHANCE FOR LIGHT SNOW WITH THE WAA
SATURDAY NIGHT OVER MUCH OF THE CWA...BUT AMOUNTS WILL BE LIGHT. WE
ADDED/INCREASED POPS ALONG THE NORTH SHORE SATURDAY NIGHT INTO
SUNDAY DUE TO A LONG FETCH WITH MARGINAL DELTA-T/S. THE AIR MASS DOES
NOT LOOK AS DRY AS EARLIER RUNS...AND GIVEN LONG FETCH AND SOME
SYNOPTIC LIFT...SOME LES CAN`T BE RULED OUT.
EMPHASIS SHIFTS TO THE APPROACHING STORM FOR SUNDAY NIGHT INTO
TUESDAY. THERE HAS BEEN A GENERAL SHIFT NORTH WITH THE EXPECTED
TRACK OF THE SYSTEM. THE GEM/NAM ARE QUITE A BIT FARTHER
NORTH...WITH THE GFS NOW THE MOST SOUTHERLY. HOWEVER...SEVERAL OF
THE GFS ENSEMBLE MEMBERS DO SHOW THE LOW/PRECIP QUITE A BIT FURTHER
NORTH THAN THE OPERATIONAL RUN. PICKING ONE PARTICULAR SOLUTION AT
THIS TIME IS JUST TOO DIFFICULT. WE DID INCREASE POPS SUNDAY NIGHT
INTO MONDAY...MAINLY ACROSS OUR SOUTHERN CWA.
THERE WILL BE A CHANCE FOR SOME LAKE EFFECT SNOW FROM ABOUT SILVER
BAY TO THE TWIN PORTS...AND ALONG THE SOUTH SHORE SUNDAY NIGHT INTO
TUESDAY. 850MB TEMPS WILL REMAIN FROM -10C TO -12C...WITH A PRETTY
GOOD FETCH. MOISTURE WILL BE AN ISSUE DEPENDING ON THE TRACK OF THE
LOW.
HOPEFULLY WE`LL SEE BETTER AGREEMENT WITH THE MODEL RUNS TODAY AND
INTO THE WEEKEND...AND WE CAN ADJUST THE FORECAST FROM THERE.
&&
.POINT TEMPS/POPS...
DLH 26 2 28 13 / 10 0 10 30
INL 23 -9 30 10 / 0 0 20 30
BRD 29 4 30 16 / 0 0 20 20
HYR 27 -1 28 0 / 0 0 10 10
ASX 25 6 28 5 / 0 0 10 10
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
SHORT TERM...DAP
LONG TERM....GROCHOCINSKI
AREA FORECAST DISCUSSION
NWS MILWAUKEE/SULLIVAN WI
326 PM CST FRI MAR 1 2013
.SHORT TERM...
TONIGHT AND SATURDAY...FORECAST CONFIDENCE IS MEDIUM
BAND OF LIGHT SNOW SHOWERS HAS WEAKENED TO FLURRIES FROM NEAR
MADISON TO FOND DU LAC...AND SHOULD CONTINUE TO WEAKEN THROUGH
SUNSET...AS DRIER AIR WORKS INTO THE AREA. ANY FLURRIES SHOULD
DISSIPATE ACROSS MOST OF THE REST OF THE AREA SHOULD DISSIPATE BY
EVENING AS WELL...EXCEPT FOR LIGHT LAKE EFFECT SNOW SHOWERS/FLURRIES
NEAR THE SHORELINE EAST AND SOUTHEAST OF MILWAUKEE.
MARGINAL DELTA T VALUES OF 12 TO 14 DEGREES CELSIUS...FAVORABLE
NORTH NORTHEAST FETCH...AND MODEST LOW LEVEL CONVERGENCE MOVING
TOWARD THIS AREA THIS EVENING MAY BRING THIS BAND ONSHORE. HRRR AND
LOCAL WRF 4KM MODELS TRY TO DO THIS...THEN TRY TO SHIFT IT BACK
OFFSHORE AFTER 06Z SATURDAY. LEFT SCATTERED POPS FOR LIGHT SNOW
SHOWERS SOUTH OF MILWAUKEE NEAR THE LAKE TONIGHT. A FEW TENTHS OF AN
INCH COULD FALL IF THESE BANDS MAKE IT ONSHORE. LOW LEVEL FLOW
BECOMES MORE NORTHERLY SATURDAY...WHICH SHOULD KEEP THIS BAND
OFFSHORE. LEFT FLURRIES IN THE FAR SOUTHEAST...WITH LOW LEVEL
MOISTURE LINGERING WITHIN DENDRITE ZONE.
CLOUDS SHOULD GRADUALLY MIX OUT FROM NORTHWEST TO SOUTHEAST ACROSS
THE AREA TONIGHT...AND FINALLY MIX OUT IN THE FAR SOUTHEAST COUNTIES
BY SATURDAY AFTERNOON AS LAKE EFFECT CLOUDS MOVE OFF TO THE
SOUTHEAST. TEMPERATURES WILL BE BELOW SEASONAL NORMALS TONIGHT AND
SATURDAY...WITH 10 TO 15 INLAND WITH AT LEAST PARTIAL CLEARING...AND
UPPER TEENS WITH MORE CLOUDS IN THE FAR SOUTHEAST COUNTIES NEAR THE
LAKE. HIGHS IN THE MID TO UPPER 20S SEEM REASONABLE FOR SATURDAY.
SATURDAY NIGHT THROUGH TUESDAY...FORECAST CONFIDENCE MEDIUM
SFC HIGH PRESSURE TO SETTLE OVER THE REGION SAT NT AND SUN. A
SHORTWAVE TROUGH WILL TRACK DUE SOUTH FROM CANADA TO LOWER MI FOR
THIS TIME PERIOD BUT AIRMASS REMAINS DRY. MID TO HIGH CLOUDS WILL
BE INCREASING LATE SAT NT INTO SUNDAY WITH WARM ADVECTION ALOFT
AND RIDGING. RIDGING IS IN RESPONSE TO A STRONG SHORTWAVE TROUGH
OVER MT THAT WILL MOVE TO THE MIDDLE MS RIVER VALLEY ON TUE AND TO
THE EAST COAST FOR WED. RUN TO RUN MODEL CONSISTENCY IS
STRUGGLING WITH THE EXACT TRACK OF THE STRONG SHORTWAVE
TROUGH. HOWEVER...LATEST MODELS HAVE FAIRLY GOOD AGREEMENT MINUS THE
OUTLIER OF THE NAM. WILL STILL ACCOUNT FOR THE LACK OF RUN TO RUN
CONSISTENCY HOWEVER AND FORECAST SMALL CHANCES OF LIGHT SNOW
BEGINNING LATE SUN NT OVER SOUTH CENTRAL WI AND THEN SPREADING
EAST WITH CHANCES OF LIGHT SNOW THROUGH TUE NT. EXPECT THE MAIN
AXIS OF SNOW TO REMAIN MOSTLY ACROSS IA AND IL WITH BEST CHANCES
FOR THE NRN PORTION OF THE SNOW TO AFFECT SRN WI ON TUE.
WENT WITH FAIRLY COLD TEMPS SAT NT AND SUN NT DUE TO GOOD
RADIATIONAL COOLING WITHIN A POLAR HIGH. THE CLOUDS WILL ARRIVE TOO
LATE ON SAT NT FOR MUCH EFFECT AND ONLY PTLY CLOUDY CONDITIONS
ARE FORECAST FOR SUN NT. 925 MB TEMPS SUGGEST HIGHS WILL BE AROUND
30F FOR SUN-TUE.
.LONG TERM...
WEDNESDAY THROUGH FRIDAY...FORECAST CONFIDENCE MEDIUM
RIDGING ALOFT IS EXPECTED FOR WED INTO THU AS A LONGWAVE POLAR
TROUGH MOVES INTO THE WRN USA. AT THE SFC...POLAR HIGH PRESSURE
WILL PREVAIL DURING THIS TIME BUT IT MAY MOVE EAST BY THU
AFTERNOON ALLOWING SLY WINDS TO DEVELOP WITH MILDER TEMPS. BELOW
NORMAL TEMPS ARE EXPECTED BEFOREHAND. A SHORTWAVE TROUGH AND LOW
PRESSURE AREA WILL THEN MOVE NEWD THROUGH THE NRN PLAINS AND MN
FOR THU AND THU NT WITH SLIGHT CHANCES OF LIGHT SNOW OVER SRN WI
DUE TO WARM ADVECTION. SLY WINDS WILL CONTINUE ON FRI AS THE LOW
TRACKS ENEWD ACROSS ONTARIO CANADA. THUS MILD HIGH TEMPS IN THE
40S ARE EXPECTED.
&&
.AVIATION/00Z TAFS/...
FOR MADISON AND WAUKESHA TAF SITES...EXPECT FLURRIES TO LINGER UNTIL
AROUND 00Z SATURDAY. VFR VISIBILITIES ARE EXPECTED...WITH CEILINGS
REMAINING BELOW FUEL ALTERNATE THRESHOLDS LATE THIS AFTERNOON AND
PERHAPS THROUGH EARLY THIS EVENING...BEFORE DRIER AIR MIXES OUT THE
CEILINGS LATER THIS EVENING INTO EARLY SATURDAY. GUSTY NORTH
NORTHEAST WINDS LATE THIS AFTERNOON WILL DIMINISH THIS
EVENING...WITH MODEST NORTH WINDS THROUGH SATURDAY.
FOR MILWAUKEE AND KENOSHA TAF SITES...EXPECT LIGHT LAKE EFFECT SNOW
SHOWERS/FLURRIES TO LINGER THROUGH MOST OF TONIGHT...BUT DIMINISH IN
AREAL COVERAGE. A FEW TENTHS OF AN INCH OF ACCUMULATION ARE POSSIBLE
WITH ANY PERSISTENT LIGHT SNOW BANDS...MAINLY AT KENOSHA. MAINLY VFR
VISIBILITIES EXPECTED.
CEILINGS REMAIN BELOW FUEL ALTERNATES THROUGH MOST OF
TONIGHT...BEFORE MIXING OUT BY MID TO LATE SATURDAY MORNING WITH
DRIER AIR MOVING INTO THE AREA. GUSTY NORTH WINDS LATE THIS
AFTERNOON WILL REMAIN SOMEWHAT GUSTY TONIGHT INTO EARLY
SATURDAY...REMAINING NORTHERLY ON SATURDAY.
&&
.MARINE...
SMALL CRAFT ADVISORY HAS BEEN EXTENDED UNTIL 09Z SUNDAY ACROSS THE
NEARSHORE WATERS OF LAKE MICHIGAN. TIGHT PRESSURE GRADIENT WILL
REMAIN ACROSS THIS AREA INTO SATURDAY MORNING...BEFORE GRADUALLY
RELAXING DURING THE AFTERNOON. GUSTY NORTH WINDS OF 15 TO 25 KNOTS
WITH GUSTS TO AROUND 30 KNOTS ARE EXPECTED THROUGH TONIGHT...THEN
SLOWLY DECREASE ON SATURDAY.
HIGH WAVES OF 6 TO 9 FEET THIS EVENING WILL GRADUALLY SUBSIDE
THROUGH SATURDAY NIGHT...AS WINDS REMAIN NORTH BEFORE BACKING
NORTHWEST.
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 3 AM CST SUNDAY FOR LMZ643>646.
&&
$$
TONIGHT/SATURDAY AND AVIATION/MARINE...WOOD
SATURDAY NIGHT THROUGH FRIDAY...GEHRING
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
1130 AM CST FRI MAR 1 2013
.SHORT TERM...TODAY THROUGH SUNDAY NIGHT
308 AM CST FRI MAR 1 2013
POTENTIAL FOR ACCUMULATING SNOW SUNDAY NIGHT AND HEADING INTO THE
LONG TERM PERIOD.
CURRENTLY AS OF 09Z...WATER VAPOR LOOP AND RAP 500MB HEIGHT ANALYSIS
SHOWED RIDGING OVER THE WESTERN U.S. INTO ALBERTA AND GENERAL BROAD
TROUGHING OVER THE EAST HALF OF THE U.S.. THE FORECAST AREA SITS IN
A NON-DESCRIPT FLOW WITHIN THIS BROAD TROUGH...DUE TO THE MAIN JET
FLOW CONFINED OVER THE WESTERN DAKOTAS...AND AN UPPER LOW STUCK OVER
NEW ENGLAND. THIS NON-DESCRIPT FLOW HAS RESULTED IN THE VERY SLOW
SURFACE PATTERN PROGRESSION...WITH THE AREA STILL UNDER CYCLONIC
FLOW AROUND LOW PRESSURE IN NEW ENGLAND. A TROUGH EXTENDING WEST
FROM THE LOW EXTENDS WEST NEAR I-80 TO DES MOINES...THEN TO THE
NORTHWEST TO FARGO. SLOWLY DRIER AIR IS ADVECTING SOUTHWARD INTO THE
CYCLONIC CIRCULATION FROM HIGH PRESSURE OVER HUDSON BAY...RESULTING
IN CLEARING OVER NORTHERN LAKE SUPERIOR INTO THE NORTHERN 2/3 OF
MINNESOTA. HOWEVER...THE 00Z MPX AND GRB SOUNDINGS STILL SHOW A 50MB
SATURATED LAYER STUCK AROUND A COLD FRONTAL INVERSION SITTING AT
825MB. THUS...STRATUS STILL COVERS THE AREA. THIS STRATUS COMBINED
WITH A 5-10 KT NORTHEAST WIND HAS KEPT TEMPERATURES MAINLY IN THE
20S...DESPITE 850MB TEMPS AROUND -11C OR 1 STANDARD DEVIATION BELOW
NORMAL PER 00Z RAOBS.
SHORT TERM HIGHLIGHTS / CONCERNS:
1. WHEN WILL IT CLEAR
THIS IS A TWO PART ISSUE. FIRST AND MORE IMPORTANTLY IS THE GENERAL
STRATUS DECK IN PLACE. 01.00Z NAM WAS SURPRISINGLY TOO AGGRESSIVE
WITH CLEARING...SUGGESTING BASED ON 850MB AND 900MB RH FIELDS THAT
LOCATIONS NORTH OF I-90 WOULD BE CLEAR RIGHT NOW. LATEST RAP 850MB
AND 900MB RH GUIDANCE SEEMS TO HAVE A BETTER HANDLE ON THE LOW
CLOUDS...GRADUALLY CLEARING LOCATIONS NORTH OF I-90 NORTH TO SOUTH
THROUGH 21Z. A COMBINATION OF DAYTIME MIXING AND A STRONGER SURGE OF
DRY AIR FROM NORTHERN ONTARIO APPEARS TO BE AIDING IN THIS CLEARING.
SOUTH OF I-90...THE LOW CLOUDS MAY NOT DISSIPATE UNTIL SOMETIME
DURING THE EVENING. THE SECOND PART OF THE CLEARING ISSUE IS IN THE
UPPER LEVELS WHERE SCT-BKN CIRROSTRATUS EXISTS OVER THE AREA. THE
NON-DESCRIPT UPPER LEVEL FLOW WOULD SUGGEST CLEARING OF THE CIRRUS
WILL BE PROBLEMATIC. NAM/RAP 500-400MB RH FIELD CONFIRM THIS AS WELL
WITH MUCH OF THE AREA DOMINATED BY SCT-BKN CIRROSTRATUS THROUGH THE
DAY TODAY...ESPECIALLY OVER THE WESTERN HALF. IT LOOKS LIKE WE
FINALLY CAN CLEAR THESE HIGH CLOUDS OUT TONIGHT INTO SATURDAY
MORNING AS THE UPPER RIDGE OVER THE WESTERN U.S. BEGINS PROGRESSING
EAST.
2. TEMPERATURES TODAY THROUGH SATURDAY NIGHT
THE STRONGER NOW EARLY MARCH SUN CAN DEFINITELY WARM TEMPERATURES
UP...EVEN UNDER AN ENVIRONMENT OF COLD 850MB TEMPS...LIKE THOSE
TODAY AROUND -11C. HOWEVER...WITH ONLY PARTIAL CLEARING OVERALL
NORTH OF I-90...IT LOOKS TOUGH TO GET TEMPERATURES TO OR ABOVE
FREEZING. NAM 2 METER AND MET GUIDANCE LOOKS A BIT TOO OPTIMISTIC...
GIVEN THE FACT THAT IT HAS CLEARING MUCH EARLIER THAN WHAT WILL
OCCUR. HAVE LEANED MORE TOWARDS MAV/ECMWF/GEM GUIDANCE AS A RESULT.
RELATIVELY COOL CONDITIONS TODAY COMBINED WITH CLEARING TONIGHT AND
WINDS CALMING WITH HIGH PRESSURE BUILDING IN SETS THE STAGE FOR A
DECENT RADIATIONAL COOLING NIGHT. THUS...STAYED TOWARD THE COOL END
OF GUIDANCE. MUCH MORE SUN ON SATURDAY WITH SIMILAR 850MB TEMPS WILL
YIELD JUST A SLIGHTLY WARMER DAY. THE SURFACE HIGH PRESSURE RIDGE IS
PROGGED TO REMAIN NEARBY SATURDAY NIGHT...WHICH AGAIN PUTS A GOOD
RADIATIONAL COOLING NIGHT IN FOCUS. HOWEVER...MID AND HIGH CLOUDS
LOOK TO INCREASE COMING THROUGH THE UPPER RIDGE BUILDING TOWARDS US.
THUS...WE SHOULD NOT GET AS COOL AS TONIGHT. STILL...TIMING OF THE
CLOUDS IS EVERYTHING AND TYPICAL COLD SPOTS IN WISCONSIN COULD STILL
END UP PLUMMETING. THUS...FOR THE TYPICAL COLD SPOTS LEANED MORE
TOWARDS THE COLDER SIDE OF GUIDANCE FOR THEM.
3. POTENTIAL FOR WARM ADVECTION PRECIPITATION SUNDAY/SUNDAY NIGHT
MODELS ARE PROGGING THAT A POTENT UPPER TROUGH...CURRENTLY PRESENT
NEAR 45 N / 150W WELL SOUTH OF THE GULF OF ALASKA...WILL CRASH
THROUGH THE UPPER RIDGING BUILDING TOWARDS THE FORECAST AREA DURING
THE WEEKEND. BY 12Z SUNDAY...GOOD MODEL AGREEMENT EXISTS THAT THIS
POTENT UPPER TROUGH...PERHAPS IN THE FORM OF A CLOSED LOW...SHOULD
BE OVER WASHINGTON STATE. THERE STILL REMAINS SOME DISAGREEMENT ON
THE TRACK OF THE POTENT UPPER TROUGH AFTERWARDS...BUT THERE DOES
APPEAR TO BE A CONVERGING SOLUTION. BY 12Z MONDAY...THE TROUGH
SHOULD EXIST SOMEWHERE BETWEEN ENTERING WESTERN SOUTH DAKOTA
/SLOWER 01.00Z ECMWF/ TO SOUTHEAST SOUTH DAKOTA /FASTER 01.00Z NAM/.
THE SPEED FACTOR APPEARS TO BE RELATED TO HOW POTENT A SHORTWAVE IS
DROPPING THROUGH MICHIGAN ON SUNDAY...THE MORE POTENT THE SLOWER THE
UPPER TROUGH COMING ACROSS THE NORTHERN ROCKIES WILL BE. THIS
FORECAST IS GOING TO TAKE A CONSENSUS APPROACH TO THE 01.00Z
GUIDANCE...GIVEN THE CONVERGING TREND BUT AT THE SAME TIME ALLOWS
FOR A LITTLE CONTINUITY.
DETAILS...AS THE POTENT TROUGH DIGS INTO THE NORTHERN ROCKIES ON
SUNDAY...LOW PRESSURE DEEPENS DOWNSTREAM OVER SOUTH DAKOTA AND
NEBRASKA. IN TURN...WARM ADVECTION INTENSIFIES...DEVELOPING A MASS
OF MID CLOUDS FROM THE DAKOTAS INTO THE FORECAST AREA. THE 00Z
GFS/UKMET/CANADIAN ALL DEVELOP SOME LIGHT PRECIP WEST OF THE
MISSISSIPPI RIVER BETWEEN 18-00Z...BUT UNSURE IF THIS IS GOING TO
REACH THE GROUND AS REFLECTED BY THE 00Z ECMWF. INCLUDED JUST A 20
PERCENT CHANCE OVER SOUTHEAST MN FOR NOW. CHANCES INCREASE
EVERYWHERE SUNDAY NIGHT...ESPECIALLY WEST OF THE MISSISSIPPI
RIVER...ASSOCIATED WITH THE TROUGH PUSHING EAST AND MORE IMPORTANTLY
THE LOW TO MID-LEVEL FRONTOGENESIS ZONE STRENGTHENING. INCREASED
CHANCES TOWARD 60 LATE IN THE NIGHT WEST OF HWY 52.
ANOTHER CONCERN TO WATCH IS A POTENTIAL WARM LAYER ACCOMPANYING THIS
SYSTEM. THE FASTEST 01.00Z NAM WOULD SUGGEST THAT THE PRECIPITATION
SUNDAY AFTERNOON OR EVENING WOULD START AS SLEET SAY IN THE AUSTIN
AREA. HOWEVER...SINCE A COMPROMISE APPROACH WAS FOLLOWED...ANY MIXED
PRECIPITATION TYPE TRANSITION ZONE SHOULD STAY OFF TO THE WEST.
.LONG TERM...MONDAY THROUGH THURSDAY NIGHT
308 AM CST FRI MAR 1 2013
MAIN CONCERN/FOCUS OF THE LONG TERM PERIOD REMAINS ON THE POTENT
UPPER TROUGH IN SOUTH DAKOTA EARLY MONDAY. THE 01.00Z
ECMWF/UKMET/CANADIAN AND GFS ENSEMBLES ARE ALL IN GOOD AGREEMENT
THAT THIS TROUGH WILL CLOSE OFF AND BE IN/NEAR WESTERN IOWA BY 12Z
TUESDAY. NOTE THAT THE 01.00Z GFS ALSO CLOSES IT OFF...BUT IS MUCH
MORE PROGRESSIVE...DOWN IN SOUTHERN MISSOURI AT 12Z TUESDAY. GIVEN
THE PREDOMINANCE OF SLOWER SOLUTIONS...DISCOUNTED THE GFS. THESE
SLOWER SOLUTIONS MEAN THAT A LOW TO MID-LEVEL FRONTOGENESIS BAND
WILL GET STUCK. WHEREVER THIS OCCURS THERE COULD END UP BEING SOME
DECENT SNOW ACCUMULATIONS. RIGHT NOW IT APPEARS THE BAND WOULD SET
UP FROM NORTH DAKOTA INTO SOUTHEAST MN AND INTO EASTERN IOWA. RAISED
PRECIPITATION CHANCES IN THIS AREA 20 PERCENT FROM THE PREVIOUS
FORECAST...AND MAY NEED TO BE RAISED MORE IF TRENDS CONTINUE.
A LONGWAVE TROUGH IS FORECAST TO TRY TO ENTER THE WEST COAST TUESDAY
NIGHT...WHICH MODELS HAVE SHOWN FOR AWHILE. THIS TROUGH WILL HELP
BUILD AND PUSH RIDGING EASTWARD...CAUSING THE UPPER LOW OVER WESTERN
IOWA TO SHIFT SOUTHEAST...AND PUSH THE LOW TO MID-LEVEL
FRONTOGENESIS CIRCULATION EASTWARD. THUS...THE SNOW MAY END UP
OVERSPREADING MUCH OF THE AREA ON TUESDAY AND ADDED 20-40 PERCENT
CHANCES AS A RESULT. EVEN ADDED A 20 PERCENT CHANCE OVER THE
SOUTHEAST 1/3 TUESDAY NIGHT.
WHEN ALL IS SAID AND DONE FROM THE SUNDAY NIGHT THROUGH TUESDAY
PERIOD...WE COULD BE LOOKING AT EITHER A LONG DURATION ADVISORY
EVENT OR EVEN WARNING IF THE 01.00Z CANADIAN ENDS UP RIGHT.
DEFINITELY NEED MODELS TO COME TO BETTER AGREEMENT AND MORE
DETAILS WORKED OUT BEFORE SPECULATING ON SNOWFALL AMOUNTS. 01.06Z
NAM CONTINUES TO SHOW AN AGGRESSIVE QPF SCENARIO SIMILAR TO THE
CANADIAN...ALONG WITH SPREADING PRECIPITATION FARTHER EAST. QUICK
LOOK AT THE 01.00Z ECMWF ENSEMBLE MEAN ALSO APPEARS TO BE IN-LINE
WITH THE NAM/CANADIAN IN TERMS OF 500MB HEIGHT AND MSLP. AS
MENTIONED...PLENTY OF DETAILS TO WORK OUT.
QUIET WEATHER ROUNDS OUT THE REST OF THE WEEK WITH MODELS IN GOOD
AGREEMENT SHIFTING THE UPPER RIDGE INTO THE FORECAST AREA. THIS
SHOULD BRING TEMPERATURES BACK UP TO NEAR OR POSSIBLY EVEN ABOVE
NORMAL BY THURSDAY. IF THE 01.00Z GFS IS CORRECT...WE COULD EVEN BE
LOOKING AT A RAIN/SNOW MIX THURSDAY NIGHT AS IT EJECTS OUT A
SHORTWAVE FROM THE WESTERN TROUGH THROUGH/NEARBY THE FORECAST AREA.
&&
.AVIATION...THROUGH 18Z SATURDAY
1130 AM CST FRI MAR 1 2013
HIGH PRESSURE WILL GRADUALLY PUSH INTO THE AREA FROM THE NORTHWEST THROUGH
THE PERIOD. THE MVFR/VFR STRATUS DECK WILL SLOWLY RISE THROUGH THE AFTERNOON
HOURS AND EVENTUALLY CLEAR OUT THIS EVENING. EXPECT THE LOWEST
CEILINGS TO RANGE FROM 025-035K KFEET THROUGH 00Z...WITH CLEAR
SKIES EXPECTED AFTER 06Z-08Z.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
308 AM CST FRI MAR 1 2013
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...AJ
LONG TERM...AJ
AVIATION...RABERDING